This was a long time ago but I wanted to share because I'm not sure if I went over the line or not

I was on a train in Europe and I was just minding my own business searching restaurants. A kid walks up to me and makes the slited eye gesture and says a stuff like 'We used to own your kind' and 'How did you manage to pay for the ticket'. Mom doesn't do anything and no one steps up.

I say 'Oh, look at little Hitler Junior' and the mom suddenly gets offended at me and gets off at the next station.

I mean, I know I shouldn't mention nazis and Hitler since it's a very sensitive topic. But the kid started it first...not sure if I stepped over the line or if I did an understandable thing.