I think of it the same way alcohol makes people do things they normally wouldn't do. Mania also lowers your inhibitions, which is why alcohol and mania don't mix.
*trigger warning* Not sure if it needs it, but just to be on the safe side...

Some people say they would have never raped someone if they weren't under the influence, but I firmly believe that alcohol simply makes people more likely to act on things they already have the capacity to do. I think mania operates in the same way.

I guess, I could see severe, severe mania being somewhat of a wildcard, but for the most part, I think mania just lowers your inhibitions the same way substances do, which again, is why mania and substances DO NOT MIX.