In truth, you should have given him a warning after the first incident, and then booted him after the second (2nd Round). This IS what my Clan does. We then report the individual to Bungie. The problem with how you handled it, isn't that you booted him, but WHEN. By booting him at the reward locale, it does nothing but make YOU look like an ass. In the future, set your rules at the beginning. Advise the LFG Guardian that if they don't participate they will be booted. This will save you from getting under Bungie's ban hammer.