That's a somewhat
adolescent outlook on adulthood, though, isn't it? And aptly so, since
Human Traffic is a movie about a group of people who will tell any lie, espouse any
bullshit philosophy, and
inject any substance in order to stop themselves growing up.
People are very rarely as stupid as you think.
Only 7% of communication is verbal**.
Combine these two statements and what do you get? Correct - people probably know what you're thinking of them anyway. They might return the compliment of your discretion by not verbalising their responses, but they know nonetheless. In fact, I've found that one of the side effects of maturity for me has been a realisation of just how much nonverbal communication is going on around me all the time. So rather than knowing less about the opinions and feelings of people around me I now know more.
And still the world goes on, people get jobs and thankfully get laid, too (although in some cases not quite as much as is good for them).
** OK, I made that statistic up. But whatever the numbers are, the principle remains the same - just because you don't say something doesn't mean nobody can guess you're thinking it.