Sweeping generalisation re teacher nationality

[Hillbilly]

In a conversation last night with DD (18) and H, about an issue DD had at college this week with a tutor. H referenced tutor's nationality as a probable factor in the way they dealt with the issue (poorly). I pulled him up in this saying it was a sweeping generalisation and had no relevance to the situation.
Minor argument (not heated) followed, in front of DD, which obv distracted momentarily from actual issue under discussion and later I was accused of BU and wrong by H, and that I should not have said it in front of DD, that if I had a problem with his point I should have spoken to him alone later. I disagreed saying I didn't want this kind of generalisation to be seen by DD as normal or acceptable.
Who was BU?

@Catza all very good points you make, and you are probably right......

But that’s not true at all, anyone who’s worked with various nationalities will tell you there’s different social traits that we might not be accustomed to, for instance many Italians really do shout and talk over one another, and have very animated what seems arguementive conversations but they see it as normal.
whereas in my household that wood be classed as an arguement I understand for them it’s normal.