The truth can be embarrassing

When I was still in school we had a boy in our class who we did not like as he was mean.
One day I and a friend from my class were on the train sitting opposite each others.
I said - Really what an idiot our classmate X is. My friend did not respond which I thought was strange so I continued on the same subject. - X is such an awful person isn´t he? Still not an answer from my classmate not even a nod. It turned out that the lady sitting beside me was X´s mother and I did not know her but my classmate knew who she was. There would be no doubt about who X was as he had an extremely unusual name. Really embarrassing but then again what I said was the truth her son was not a good person.