BSD/MIT allows you to take code without any obligation to contribute back.

Using code that is freely given is not in any sense stealing.

Only if you think taking the work of others and profiting from it without contributing anything back is fine.

The people who did the work obviously think it's fine, otherwise they wouldn't have licensed it under such a permissive licence.

Certainly. MIT/BSD more or less says: steal away (but retain this license notice). In some cases that's desirable.

Is it stealing if somebody gives you a present and you accept it?

I am not going to debate whether it's "fine", but it's certainly not stealing. If I make someone a beautiful necklace and they sell it in an auction, I might wish they hadn't done that with my gift - but they haven't stolen anything either.