This should be enough to not get kicked at the beginning. You'll not be considered as "just another team killer who's not even using chat". Also, people often feel bad about kicking someone whos chatting.

Taking flamer is usually enough to be kicked immedietly from lobby. It's a really good weapon when you're playing solo, with one or two players. But more experienced people hate this weapon because it's very easy to ignite teammates. Also, flamer users are usually rushing foward and triggering all spawners so his teammates need to deal with them and often dying. If there's more than 3 players, just take a different weapon. But if you really want to use flamer, then stay last and cover back. And of course, write this on chat so other players will know.

If it's hardcore, then you should think about taking weapons that are safer to use (like Tesla Cannon)

Like with flamer, just stay last and cover back. This way you'll minimize the chance of killing teammates.

Say sorry and take Tesla Cannon next round. You don't need to play with Tesla your whole life but as a beginner just avoid team kills until people will start recognizing you.

If they kicked you out after all this, then you probably faced a real ♥♥♥♥♥♥♥♥s and it's not worth to play with them anyway. :P

Have fun!