Kicking people for not being good is just bad. Yeah, noobs are a pain when they're on your team, especially in Tremulous where feeding is a problem. But for most cases, at least when I've played, you can votekick people who are really feeding or newbies who won't listen to reason.
But I really don't like automatic newb kicking, a.k.a. "winner stays on". If you're a really competitive player, than sure, having a newbie on your team sucks. Ideally you shouldn't have one and there are so many players that there's some kind of matchmaking system, or ranked/unranked servers. But the instant you start alienating new players who are trying out the game that you're playing is the instant you start strangling your game to death.
New players are, in a sense, the next generation. When you're small community you can't afford to give up your ability to grow. Can you imagine if that newbie rule was in place, 1.2 was released, and a bunch of newbies joined, but were subsequently kicked out of every other round? Most would just stop playing then and there. They don't want to be second class citizens, then ones you want just want to suck at the game in peace.
Maybe I'm conjecturing too much. I honestly don't think that being nice can actually save Tremulous, or any other game, by itself: the developers are the natural leaders who make stuff happen, and it is hard to do anything without your leaders.
Also, "loser stays on" is also kind of a bad idea, as it's really easy to fake being worse than you actually are just so that you can stay on. It wouldn't be as great in Tremulous as you'd be directly making the other team stronger, but I can still imagine people who would rather lose than be forced to not play because they're too good. The point of people playing your game is so that they can play your game! Not sit out...