It's really easy to be an ass online. People will say insanely rude and offensive things to you. They will say things in front of 1,000 readers that they wouldn't dare say to your face.
Ignore them.
Block them, delete their comments, unsubscribe, stop reading.
If someone was rude, loud and insulting, you'd throw them out of a restaurant, store, party, or your living room. You'd hang up the phone. There's no need to lower your standard online.
If you encourage them — you'll get what you ask for. The web will be a place where the loudest, nastiest voices make it suck for everyone.
It's up to you to decide if you want the web to be a nice place. If you do, take a stand and tune out the people who can't hold a civil, polite conversation.