It was flamebait, but please let's not take the bait because a religious flamewar is not what we need here.
Ie, this isn't attacking anyone on the basis of their religion.
I'd probably say the comment could be improved by adding a link to https://en.wikipedia.org/wiki/Criticism_of_Pope_John_Paul_II instead of 'that bastard' but criticism of people that facilitate child abuse is quite reasonable and very separate from attacking members of a particular religion.
Commenters who get too sure of their moral positions tend to do a lot of this. I'm not saying the moral positions are wrong (I probably agree a lot of the time, certainly Sinead did a courageous thing, etc. etc.). But the quality of discussion this leads to is predictably poor, evokes worse from others, and tends to go straight to the bottom of the internet barrel. We're trying to not get sucked completely into that muck here—a difficult task to even partly achieve, so we need everyone's help.
The man - and the institution - facilitated and covered up the abuse and rape of countless children. Calling him a bastard seems pretty small potatoes for you to start clutching your pearls over.
People tend to respond to activating topics with intense pre-existing feelings. That's understandable—I'm not criticizing it and it would be futile to try to change it. But it does not make for curious conversation, which is what HN is for: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...
Curious conversation is about learning new things, changing one's orientation, and so on. That's one reason why the best HN threads tend to have a whimsical aspect—when a topic isn't high-stakes and one doesn't have a pre-existing position about it, curiosity is the natural state. Not so much otherwise.