The truly sad part of your post is that he felt that he had to do this via his Twitter account. Showing my age here, but social media (Facebook and Twitter specifically) is a huge part of the problem that you are describing. I would be willing to bet that the people that are saying the awful things on social media would never have the nerve to say those things to a person's face. There are no real consequences to being a hateful and rude person. It used to be that if you did say something like that to someone, they would punch you! Now other than maybe getting an account deactivated, there are no consequences.
Again in my opinion, this has caused the divisiveness and downright hate. To the point that we can't "agree to disagree" any more. It is very, very sad . . .