Would you react negatively if someone asked for your birthdate?

I remembered that about a year ago, I asked someone (an acquaintance) about his birthday...and his response was to ask for my reason.

The relation was going well and birthday is a happy event for everyone, and I thought of giving a birthday gift.

That was my only reason...but he became extremely serious and it became an awkward (unhappy) thing, because he opened up about his past issues (trauma) and ya know how it might be possible for people to do 'not good' stuff to others just by knowing the birthdate of a person.

He didn't believe my answer and he thought that there's a much deeper reason, although he gave me his birthdate in the end.

Surprisingly, up till now...I don't bother about him, and probably it's because of how that conversation went.
I had happy or funny ideas for a birthday gift before that...me being happy but he wasn't.

I have no intention of connecting or communicating with that person again, but this incident suddenly popped into my mind...and I was thinking that not everyone has a bad intention and that was an extreme reaction.

Maybe just sharing here and hear your thoughts?