Does anyone have good ways to counter these kinds of jokes?
Smile, and say, 'I'm sorry that you feel that way.' Then excuse yourself, as you have things to do.
NEVER let it get to you - the world will eat you alive.
I still deal with it at times. A couple of weeks ago a guy at work came up to me, leaned in, and whispered '...polish girls....they're all sluts.'
Being 100% polish, a speaker, reader and writer of it, still retaining that as my ethnic identity in culture and all in the U.S., with half of my family still in Poland, how can I not think that this guy is a retard? Of course he pissed me off, but F him. I smiled and said what I wrote above and then went back to work.
It's not just about being polish. If you let things get to you, then life will be tough. You need to develop some thick skin, witty comebacks, etc., to deal with life. You can't explode in these situations.