It’s very difficult to ignore such idiots. I’ve come across a couple of people in my life who continuously make idiotic or blunt comments and I’ve always ignored them. I regret not saying something to them. Some people deserve a dose of their medicine.
OP… I don’t blame your friend for getting mad at you. You commented on pics that others can see and it does make the other self-conscious.
The facebook message… I would have ignored it or written a response defending the points brought up while refraining from insulting the other person (their religion, race, etc.)… that way you still get some peace of mind that you wrote a good response and didn’t lose your dignity. Then block the guy.