Yeah, griefers are a major problem. I've been playing several matches with 2 griefers on my team, and they just wouldn't stop re-connecting and ruining the game.
And it's not just C4 trolling, they're also blocking building entrances with APCs, pushing team vehicles out of cover, spam ion/nuke beacons to cause FPS lag etc.
Something must be done about this. Server admins aren't around 24/7 and thus these idiots keep destroying the fun for everybody. Also at some point most people stopped voting or voted against a player kick since they knew it wouldn't do much anyway, which is simply a sign of resignation resulting from this problem.