I didn't downvote it, but I guess it was for asking for a source for something that at least I thought was common knowledge.

You seemed to be expressing curt disbelief of a broadly uncontroversial historical fact. Could easily be seen as trolling or an unwillingness to take the time to do some basic self-education.

Ah, I suppose it seems that way, thanks.

I really had not heard of this; which was why I asked for a source, so that I could learn of it. The request was stupidly lazy, I admit; but I think asking (if done properly) for a source is one of the things that never should be met with disapproval.

Downvoting is a bit like flipping the finger to someone, or sticking out your tongue. It's not really an argument, just a rather nasty symbol of dismay. Now watch this post get downvoted just for divulging this HN secret. ;)