Wyldkat, I hear you. My oldest is now 20 and those weird feelings of being from a different planet don't come as often now. But they do happen occasionally, and they can be very disconcerting.
As an example, my son is performing in Macbeth this week. A couple weeks ago, a college student (from a small but respected private liberal arts college) was brought in to talk to the cast. She said that she was majoring in Shakespeare. She told us a bit about the Bard; when he wrote Macbeth; when it was first performed. THEN, she went on to tell us that King James was the son of "Bloody Mary". I could hardly stand to listen to her after that. I waited politely until the end of her presentation, and then raised my hand for the comments. I said that I had a minor point to correct, and went on to say that "Bloody Mary" was Mary Tudor and she had no children. James's mother was Mary (Stuart) Queen of Scots. The young woman then said that it was Elizabeth who had no children! ARGH! I was ready to tear out my hair. So I very nicely repeated the facts, and she refused to entertain the idea that she might be wrong. She just stated that that's what she had learned in her such and such class. I had to go outside and call my nine year old daughter to vent. She was absolutely shocked that a college student who is studying Shakespeare could make such an error. DD knew the correct history when she was four or five year old.
Ms Friz, please don't ask your son to keep his enthusiasm to himself! Let him be who he is, without apology or shame. He's not showing off, he is just being himself.