The worst infighting I've yet to see was when I trained in a local MMA gym. It was run by a bunch of guys in their early to mid 20's who had all the answers. They were constantly arguing and back biting, lying to each other and the students. Hell, the head guy even had an affair with the wife of the only instructor with any maturity the gym even had. I don't know if you could call this place a McDojo because there were some good sport fighters but their self defense programs were a joke (with the noted exceptions of those taught by a JKD teacher and a Wing Chun/ Wrestling teacher) and if you didn't watch it they'd separate you from sh!tloads of $ real quick. I have heard the owners motto was "Tell them anything to get 'em to sign". They were a **** egotistical crew too.

I have learned silence from the talkative, toleration from the intolerant, and kindness from the unkind; yet, strange, I am ungrateful to these teachers.
--Khalil Gibran