Poor play is a legit reason to kick somebody. Tell your friend they are not a special snowflake and to do what they are told. I really hate those people where you make a strat and they just ignore it like "I do what i want!" You find them in Titan Ex runs too when everyone stacks up and one person stands in the position everyone wants to dodge to then on the double WotL they screw everyone over >.<. I think most people would rather not play with somebody who is arrogant and not a team player. There was absolutely no reason he couldn't go in the belly except for him sulking that he didn't get to do things his own way. A full DPS team can enter and kill the belly in under 30 seconds it's not like it's a big deal to go in.