Well he is insane. So the mares will drive him into sane state of mind.

And off course. She imprisoned him into the prison of ice where he will be tormented by cold till he escapes and taking away his physical body? Not exactly a way to make someone nicer. While imprisoning does make sence but talk about kicking a stallion when his on the ground.

Heck, I still think his original punishment was a tad bit overkill, compared to how bigger villains were punished.