This morning, I dropped my son off at pre-school, and he introduced me to one of his new friends. He then, loudly, and right in front of this friend, proceeded to explain how this child "gets upset all the time about everything" and "constantly complains". While I don't know if this is true or not (my son has a tendency to fixate onto negative behavior in others to a sometimes obsessive degree), I don't believe it matters. I simply want my son to understand that saying things like that are rude, and potentially hurtful.
I tried telling him, on the spot, to stop saying those things, because they weren't nice, and he kept interrupting me to explain that it was true ("but he does!").
I understand that "tact" is a subject some people never fully master, so I don't expect my 4 year old to fully understand it immediately, but I would like to see what can be done to improve his basic understanding of the concept.
How normal is this behavior? Is there anything I can do to curtail it, or, better yet, avoid it altogether?