Upto a point I agree, and that's what I did.
Unlike my father though, I try to encourage questioning and challenge from my kids. If they wonder about something, they'll ask.
When they first asked me about the two lesbian women I mentioned earlier, it was to ask why it was wrong, since that's what some other little kids had told them.
Kids...or mine at least...see the world around them. Hajibs, lesbians, homeless people, mentally ill, drugs, whatever...they do question it, and they have done so from a very young age.
I never quite get the 'let kids be kids' angle. By their nature, kids are endlessly curious. Letting kids be kids means you'll get a million questions about everything under the sun.
Often...and I don't mean you here, I'm just speaking generally...when people say 'let kids be kids' they're talking about sheltering them from the world they live in, and quelling their natural curiosity with half answers, or even untruths.
I've seen it a lot. Death is a classic topic where this happens but adults commonly seem to want to 'protect' kids from being kids in my experience.