Also called Peer Pressure, Conformism, Ostracism fallacy. It is similar to Appeal to Popularity.
The Bandwagon is a fallacy in which a threat of rejection by one's peers (or peer pressure) is substituted for evidence in an "argument."
It has the following form:
This line of "reasoning" is fallacious because peer pressure and threat of rejection do not constitute evidence for rejecting a claim.
It should be noted that loyalty to a group and the need to belong can give people very strong reasons to conform to the views and positions of those groups. Further, from a practical standpoint we must often compromise our beliefs in order to belong to groups. However, this feeling of loyalty or the need to belong simply do not constitute evidence for a claim.
Joe: "Bill, I know you think that 1+1=2. But we don't accept that sort of thing in our group. "
Bill: "I was just joking. Of course I don't believe that."
It is clear that the pressure from Bill's group has no bearing on the truth of the claim that 1+1=2.
Bill says that he likes the idea that people should work for their welfare when they can. His friends laugh at him, accuse him of fascist leanings, and threaten to ostracise him from their group. He decides to recant and abandon his position to avoid rejection.
Bill: "I like classical music and I think it is of higher quality than most modern music."
Jill: "That stuff is for old people."
Dave: "Yeah, only real woosies listen to that crap. Besides, Anthrax rules! It Rules!"
Bill: "Well, I don't really like it that much. Anthrax is much better."
Bill thinks that welfare is needed in some cases. His friends in the Young Republicans taunt him every time he makes his views known. He accepts their views in order to avoid rejection.
While it is widely used in whatever group one may belong, at work, in political parties, with friends, etc., it is not considered nice to use peer pressure and you certainly make weak 'converts' this way.
If your opponent tries to use peer pressure, you can show that your claim have no relation with the group and/or point out that these kind of tactics are not very nice.