Late, but I don't see a problem with GMs being able to kick a player out. It'd kill my fire to have to run to a Mod every time I wanted someone out. 

now as far as people abusing it, they should certainly have a provable reason WHY they kicked said person. Perhaps having proof they have spoken with them about an issue(posting, attitude), as most are willing to fix such things is its brought up. That would cover bases ahead of time, so if it HAS to be taken to a mod everything is in order, and the GM didn't just ban you because he/she disagreed with something small. It'll also help the banned(not sure why they'd wanna go back, but hey! Masochism), where they can prove the reason is valid or not(kicked out because sexual preference, race, etc whatever the reason).