Yes, this is why I refrain from making obviously offensive jokes. It's one thing to, say, be an American and rib your friends for their favorite team they picked in Europe (I'm not going to go in to commenting on what supporter culture means in Europe from club to club because it seems quite real and tight from documentaries and first person accounts that I read and ultimately, I do not know anything to the contrary), but it's another thing to tell people to "lighten up" over possibly the greatest known human tragedy of all time, especially when you consider that, as this comment said, people could literally see blood relatives alive, today, that were killed there, if they hadn't been brutally worked to death and killed in horrifically malicious manners.
It's only 2-3 birthing generations removed from people that are young now. It wasn't even a hundred years ago. It's impact is palpable and indelible everywhere, have you ever heard people write about it?
It just doesn't seem to be something worth making fun of. Unlike, y'know, someone's choice of Mains in super smash bros: