Pitch of voice should have no bearing, and simply telling someone in a civil manner to not yell should be an easy accomplishment... But, as you've experienced, it is not. There is no fix. Online interactions, you have to deal with what you face. Best advice, if you encounter someone like this, block them, and move on. Posting awareness, ranting, that won't solve anything. People are, and will be what they are. I don't have hope for change. Just cope with it the best you can.