YDI for bathmouthing and not carring about to whom you actually talk at a new job.

Maybe you should follow one of the golden rules. " if you don't have anything nice to say don't say anything at all." Also, as advice always answer only the questions they ask. Never give to much info unless asked. You may give them more than what you should.

Never talk down a (former) professor, (former) boss or actually...any other person. You never know when you might need them or to whom they are related. Karma always comes back.

Don't talk about people behind their backs unless you're ready to say whatever you criticizing to their face, and don't talk about your business at work no matter what; people will use it against you. Lesson learned my friend.

Meant to delete

That's why you just say: "Yes, I know him, where do you know him from", and then wait for the other person to tell you how they know them.

Bad move. If he asked if you knew the guy, it's obviously because he knows him. You should've said yes and then waited for what he said next

I saw that reply coming a mile away

...YDI, It's what you get for being a dick.

What about the Same Last name? :D