This is, in my mind, the most uniquely disgusting technique of argument I've ever encountered. No surprise that it is also often the most effective.

This is where the person of Position A is told by the person of Position B that Position A, while it may have some crude merits, is ultimately invalid, because:

A) It is immature || naïve || childish || etc.
OR
B) It is an expression of (pre/ - /post) adolescent angst.

Usually, the person will adopt a polite, yet mildly condescending tone… thereby making themselves no longer a peer, but an authority figure, artificially elevating themselves to a position that is hard to argue against without inadvertently confirming their point.

The people that are really good, or think they are, adopt a pseudo-wise stance... they pretend to be the one that attempts to "see past petty divisions" and bring unity and wisdom to the discussion… often by passing off their position as a compromise. Thus, arguing with them can easily make you seem 'immature' and 'divisive'.

This seems to be one of the most effective ways to win arguments, because although people can remain passionate about an idea or way of life in the face of overwhelming social adversity, it is much harder to maintain the same kind of passion when you are told that you will "grow out of it". Of course, it can be claimed that people are told they will "grow out of" Position A because, in fact, people usually do... what this fails to take into account is that this technique can be used against any position.

As for 'pseudo-wiseness', this is effective through the exploitation of the pre-defined stereotypes we mostly all possess; when we see some adapting the 'wise' role, we can often unconsciously attribute to them some of the respect we’ve had in the past for the few actually 'wise' people we mostly all know.

Counter:
Unless you are an extremely talented debater, the most effective recourse is usually physical violence. In fact, I believe it is the only argumentative technique where violence is necessarily the best answer. I recommend a right hook.