Yes, I only play alien. That doesn't mean aliens are OP, it just means it is what I prefer. If I wanted to play marine, there's a hundred games out there where I can be a space marine.

I'm here to eat humans. Regardless of how the team is doing, I'm going to be playing alien.

Forcing players to play in a way they don't like (such as team random) is only going to drive some people/groups away, and does nothing to enhance teamplay.