若者1 feels bad or get angry little bit, but he didn't know the definite reason. 若者2 thinks or guess that it is not so bad or it is little good, but he didn't know the definite reason. Young Japanese talk same word with different means. Could you understan my English?

You are right that the group thinking can result in an efficient mutual understanding. However, that may also end up with a disaster, depending a situation. Anyway, it is crucial to recognize that group thinking is valued so much among typical Japanese people.

Yes, it's all about reading the situation before committing to an opinion. For example: これは美味しいかも。これが好きみたい。この味は微妙。。some people think it leads to group think. But actually, I believe it helps people work better in teams. For example, many medical mistakes (and airline industry mistakes prior to recent reforms) could be avoided if more people used あいまいrather than directive language before coming to a decision.

It's my pleasure. Those are indeed common slangs. Young Japanese people often pretends not being influenced so much when they are, perhaps being afraid to be embarrassed by the somebody whom he or she speaks with, or him/herself. The true message here is that they are careful about their own reputations. If confused, just ignore さりげに or なにげに. Hope my comments are useful.

Thanks Kenta, Now it makes sense.