But I think people who kick for something like that are stupid, so if the server has enough of those people to kick you, you shouldn't play there either.
No, people who kick for things like that are smart because it has little to no way to stop and is called "spawn camping." It is looked down upon in many games.
Spawn campers deserve to be kicked from games because they reduce the enjoyability others get from the game. You might think it's fun, but if someone does it to you then you probably get rather miffed, right? Exactly. Just say no to spawn camping. Learn to play a way that actually requires skill.
What do you mean, hard to stop? I've never found ANY strategy ANYWHERE that would be hard to stop. Maybe if there'd be a map where people spawn in a single exact spot, but you're STILL invincible for long enough to flee or to go somewhere to kill the spawncamper... I don't do it because it ain't that fun, and it also ain't that useful, but I don't despise people who do. I just kill them.
Soldat respawn times are usually short enough to make spawn camping fruitless. Someone might manage to kill you once with it, but the second time you can expect it and kill the camper. And, as with any other strategy, it's much better to try and learn a counter for it than to start shouting and kicking people because of it.