He'd be more offended that you just referred to his kid as 'parasite' ..even though at the moment s/he really does feel like one. So far I've called him/her 'cabbage', 'spawn', 'junior'-I'm finding out the sex of this kid as soon as possible to find a legit name.
I think it's only because they haven't had any kids themselves, so they don't know what's in those sappy movies. Or they've been brainwashed.