A Black Belt beat by an untrained fighter?

The other day, my friend Dan and I were at my house watching a movie. About an hour later, my other friend, Mike, shows up, asking me if he could sleep on my couch since him and his girl had a bad fight. Mike was upset, and ranting & raving, and I was trying to calm him down. Dan on the other hand, was making the situation worse...he was doing his best to p*ss him off. Dan is a black belt in Tae Kwon Do, and he walks around like he's 10 ft tall, and bullet proof. Finally, Mike had enough, and told him if he wanted to go, then they'd go. Dan shot up off the couch so happily, and I bet he wish he hadn't. Mike beat the crap outta him. Dan got a few shots in, but not good ones. Also, Dan has about 60 lbs on Mike too. How did this happen? Mike has never been trained in anything at all, yet he beats down a physically fit Tae Kwon Do black belt. I was going to have Dan train me, but I guess not now.