Sometimes people who are old or middle aged forget what it's like to get an asskicking for having a big mouth. I'm not suggesting that you do it though.
Kill them with kindness...Just smile and wave.
When I was a bouncer I had a guy go "Im gonna kick your ass!!"
And I said " Oh yeah!!! Well I'm gonna give you a hug!!! Who pissed you off or hurt you today!!" in the same screaming yelling tone he did. He started crying. His wife just left him. Whenever someone says "Your stupid" Or "You look like an asshole" etc. I come back with " You look like you need a hug.!!" Sometimes this causes more trouble, so be careful.