Porn rewires the brain.

Too much and wholesome loving of an average woman is no longer enough to get it up.
And this destroys the male's ability to keep true to a woman.

The other half, half of men aren't sexually appealing to women.
So, since they destroyed the marriage contract (one man - one woman) half of the men out there get nothing. And without porn to give an outlet, these men would do something.
Probably rape would go up a little bit.
But male - male violence would go up a lot. Fighting for women.