Like all other 4chan it’s just fake news, but it would make a lot more sense to school them and what the potato famine was actually about rather than to assume they’re getting in a pissing match.
Also, in any case where coworkers are worried enough about race and politics to go to HR they’re not going to sit around and talk about ethnic stereotypes. If you’re going to sit around and talk about ethnicity and stereotypes you’ve already made a social pact that everybody isn’t going to get butt hurt and go to HR.
At my old place five of us got together once every few weeks and had a nice dinner out. It was America so nobody that was there was first generation anything. We were descendants, Irish Israeli, black, Vietnamese. If the Jewish guy would have made the potato famine joke to the Irish guy, and the Irish guy did come back with bombing hospitals, The worst outcome would be the Jewish guy would have said touche new subject and we would have continued bs about work, sports, or technology.
If it were actually a true story, maybe autistic OP thought he was returning the joke in kind. “Lol shouldn’t you be starving because the British stole all your crops but potatoes”, “lol shouldn’t you be bombing hospitals”. Seems like a fair trade if you don’t understand what was intended. Signed: an autist.