I say if the guy can't control himself, he is a danger to himself, to you, and to the life of the school itself. It's really simple. If he "goes crazy" you can politely ask him to calm down. If he won't, you simply don't spar him.
To attack him harder will probably cause him to only fight harder as well, escalating it. If you stop sparing him, he will have to tone it down or there won't be anyone else to fight.
I had someone like that at my Sifu's school. He only came in to hit someone. He didn't care that he was probably hurting them. The upper belts "gave it to him" but that's exactly what he wanted. Unfortunately when he fought lower belts, he ended up scaring them away, hurting the school. Luckily my Sifu heard our pleas and let him go. Otherwise he could have had a big lawsuit waiting in the wings.
WhiteBirch