I completely defend your stance on booting. If I'm with some randoms and one won't fall in line I boot them and if they were on my friends list they are gone. There is no room in this game for punks that can't be a team player. I had to boot a guy once in the raid because he refused to use glide for his Warlock because "I am a blink player, you can't tell me how to play." Well after the 5th time the supplicants detonated on him because he couldn't jump on the pillar he was gone forever. If you are a newbie or playing with a different team just let them know if you haven't done something and then take instruction on it. Also don't criticize the leader if they use a slightly different strategy, you may suggest an alternative but back down if they tell you they have tried it and don't like it or have had success with their current strategy. Your job as fireteam leader is to lead as many people through as you can and that may mean cutting off the problem.