As much as I hate the behavior of most clans, I don't think they should be banned here. I think wearing a tag that shows you're part of a skilled group without anyone needing to know who you are is cool. I also like how certain clans had a focus which meant you could trust a member to know some skill- it's less like this now, but PPLV was like this for stunting and flying. I don't have problems with people having friend groups, which will happen with or without clans.
I do, however, think they should actually be required to follow the rules, instead of their own bullshit. I'm still seeing clanmates on opposite teams driving each other around. To those people, grow up and play the game, instead of focusing on "dominating" with your primitive tribe. If your clan is as good as most clans claim to be, then it should be at least as much fun to play against them as with them.