The idea that there are things you're "not allowed to discuss" in modern China is, frankly, just ridiculous. People attempting to promote such an idea as the truth generally have only the most superficial "interactions" with Chinese people to go on (all too often no first-hand interactions at all) and ultimately if their ideas are challenged it tends to be the case that the root of the mistake is a mistranslation, a misunderstanding, or sadly, malice. We could call them the "Three 'M's" but that would be needlessly cute.
It is certainly true that there are, in China, as in any culture, real and ancient prejudices. In the case of China, you could mention the supposed "dirtiness" of "feet", or ideas about the relative strength of family ties, and legitimately label some of these things as cultural taboos. But that's a long way from saying one is not allowed to discuss them! Chinese exchange students often appear rude to their Western hosts by directly asking "How much do you earn?" But we wouldn't infer from that trivial cultural difference that you'd be at risk of shortening your "lifespan" if you asked that question in a Western setting (to borrow the hysterical language of the other writeup here)! It's not "forbidden" in any sense to talk about someone's wages. It's simply, in some settings, considered not the done thing.
In fact, in any non-trivial contact between Chinese and foreigners in China, at any level, it is absolutely certain that any and all topics that you may have been informed were "sensitive" or "taboo" or "forbidden" -- including Tian'anmen, Tibet, and Taiwan (the so-called Three "T"s) -- will be discussed at length and a variety of views will be expressed about them. A variety which, of course, would only surprise you if you had subscribed to the "Not Allowed!" school of thought in the first place. The conversation may indeed begin "I hear you foreigners are told you're not allowed to talk about Tibet while you're here. Is that true?! Why wouldn't you want to hear a Chinese perspective on something which intimately involves the Chinese regardless of the eventual "outcome"?"
Indeed. Why wouldn't you?
So where does this evidentially unsupportable and intellectually bankrupt idea in fact come from? As I hinted above, it usually arises from mistranslation, misunderstanding, or malice.
Mistranslation can occur both ways. If you had, in fact, in your ten-day flying tour of northern China (The Great Wall, the Terracotta Army, The Forbidden City) found yourself in a conversation with someone whose English was very 1.0, and in that conversation you'd put forth an elegant and verbose apology with respect to the Right of Self Determination, and your interlocutor had merely responded, after a long pause "You don't understand Chinese people feelings" you may feel that you've collected prima facie evidence of the contention that the issue is too tied up with emotion or history or propaganda for discussion to take place. Or in fact your opposite may simply have not understood, and snatched at your words as they flew past, and read more into your emotions than your words. It's a simple (and terribly terribly common) problem of mistranslation. Nothing whatsoever to do with any taboo, or indeed any unwillingness to discuss the difficult issues. Just a garden variety language failure. As likely to be encountered if you tried to discuss physics as politics.
Which leads directly to misunderstanding. If there's imperfect dialogue -- and lots of it! -- must there not also be misunderstandings, and lots of them? Wait a minute, you might be saying, if opportunities for misunderstanding are so numerous, why would I throw potentially contentious topics of discussion into the mix? Should I not discuss the "Three 'T's" for that reason alone? But that course of action would lead, of course, to never asking directions. A slight mispronunciation of "Where's the toilet?" in Chinese could be understood as "In which direction do I cough?" Does this mean you should pee yourself when in China? The potential for misunderstanding is no excuse for refusing to engage in all varieties of human intercourse. And if you limit yourself to simply the weather, what opportunities for actual understanding, actual communication, actual travel would there be? You have to raise your own stake to meaningfully increase the pot.
I am reminded (by UncleM) of a taxi ride we once took in Beijing in 2004, where I referred to one of the "T"s as "T-square" for the precise reason that if I said the whole name the taxi driver might overhear. Is this perhaps, tone and intention aside, an example of "Don't mention the war!" that even slightly confirms the "Not Allowed!" hypothesis? Consider the following before you answer:
Imagine you are a Australian cabbie, working in Sydney. Imagine you pick up two polite Turkish gentlemen at Kingsford-Smith who, after clearly saying where they want to go, proceed to have what appears to be a very enjoyable conversation with each other in their own language, which you don't understand. Then, in the middle of all that laughter and chatter, you hear a single "English" word which you instantly latch on to: "Gallipoli"! They say it again. They say something else. They laugh. You could be the meekest person on Earth and still want to say (even if you didn't) "Laugh about Gallipoli anywhere you like, lads, but not in my bloody cab!"
So yes, just like I wouldn't speak Chinese on a New York subway interspersed with several repetitions of the English words World Trade Center, I wouldn't speak English in the back of a Beijing taxi and repeat the word Tibet in Chinese (Xizang) several times, either. But that's just manners, not politics. That's not discussion, that's just not being a dick.
And so, to malice. What is it that leads people to make unsubstantiated claims about other cultures and/or states and/or political entities and/or the citizens thereof? Fear? Fear's cousins hatred and ignorance? If your last "update" on things in China was a half-remembered National Geographic article from the 70s replete with full-page spreads of cyclists in blue Mao suits, what would then possess you to hold forth on "Red China" as if you were some kind of authority? (Not that this stops newspaper columnists from doing exactly that!) Really, what has possessed you is that other close relative of fear: malice. It's simply malicious to interpret your own fears of the unknown as some frightening political sanction that doesn't exist. It's simply malicious to pretend you know more than you do about a vast, varied, ancient culture struggling (much as your own is) with the forces of the modern world. It's simply malicious to interpret something out of context: for example taking a bunch of virtually incoherent blog posts (in English -- there's a hint!) by angry, hyper-patriotic Chinese youth and interpreting them as a force you would encounter when actually on the ground talking to people in China.
None of this is to say that China is pure as the driven snow and/or the free-est place on Earth. China has problems. Lots of them. An inability to tolerate strong published criticism of the government clearly being one of those problems. But to suggest that the "Three T's" are not -- between private citizens, on bulletin boards, in classrooms, on campuses, in supermarkets, in taxis -- discussed at length, and freely, and foreigners shouldn't take part, is just foolishness, for all of the reasons given immediately above.
Which brings me to "Three 'T's" of my own. I'm tired of seeing mistranslation, misunderstanding, and malice passed off as some kind of "street wisdom". I'm tired of reading things that are just patently false about China. I'm tired of people interpreting their own reaction to being the "other" (a feeling anyone who doesn't "look Chinese" deals with when in China) as hostility by Chinese people. Three T's: Tired, Tired, Tired.
This lesson in communication brought to you by the elegant notion that every complex issue has a simple, incorrect cause.
Postscript: Whoever linked to If you would like to contact DMan is a genius! I only wish it had been me...