From a purely technical viewpoint, parasitism is always antagonistic/bad.

If not, it's called mutualism or commensalism. Not disagreeing with your real point, just being pedantic.

edit: to biomcgary, two points: first - i was taught that parasitism is by definition bad but actual interactions between species can fall along a spectrum of mutualistic and parasitic (and individual and specific effects may differ). second - it really ought to be moot since these terms refer interspecific interaction, right? I did a little googling before this edit, and yes, i see intraspecific brood parasitism and such... anyway, enough digression from me. I just think it's an overly-clever corruption of the actual concept of parasitism to describe a fetus as one. It's like calling a hill a parasite because it takes effort to walk up one.

You may be trying to be pedantic, but, to be meta-pedantic, your point highlights that two different conclusions are reasonable depending on the scale of analysis. At a functional level, a fetus takes nutrients from mom without returning any benefit (thus a parasite), but from the longer term perspective of evolution the relationship is mutualistic.

No benefit? What about a near-constant stream of endorphins and oxytocin?

Thanks for the 4 downvotes so far. I have a formal education in biology and my points were correct. Sorry about the tone. I guess we're valuing style over substance now.

It was a needlessly pedantic dissection of a stupid joke, one which itself should be downvoted to -4.