Cliques are a part of what gives Classic that 'special' feel back. No one can stop your friend from continuing to PvP and enjoy his time played. The thing is that if he wants to join the PvP 'community', he should expect to have to conform to some (either written or unwritten) rules that are in place in that community.
As long as he is aware of these things, he should be able to come to a decision on which way he wants to go about this.
Edit: For example, I myself would be able to find gratification in the situation your friend is finding himself in, because I have no aspiration to reach rank 12+.