I am a certified First Aider
Same here. Level C Certification.
and I didn't find that funny at all. There is nothing funny about giving CPR to begin with. Yes, if you're doing it properly, you will more than likely break someone's ribs, but making distasteful jokes about it isn't cool.
I don't know what else to tell you other than the fact that well... Its The Onion. Making crass, uncomfortable, political and dark jokes are their speciality.