Part of the purpose of sarcasm is to inject humor. Personally, I don't find anything humorous about sexual assault.
No, the purpose of sarcasm (and what distinguishes it from mere irony is having this purpose) is to mock or inflict emotional pain.
It may involve humor (irony, which sarcasm is a specific use of, is often, but not always, humorous), but that is not the purpose of sarcasm.
I just hope that the fallout doesn't begin and end with Prince Andrew and Larry Summers.
But I believe there are some subject matters including sexual assault and more specifically pedophilia that are pretty much never in good taste or useful to parody. Apparently this position is somewhat outspoken here.
Swift's Modest Proposal mentions eating babies which is very obviously an extreme behavior that is not tolerated by anyone anywhere, which is a distinct contrast to sexual assault which has victims in the millions if not billions.
Also just to note that the comment I replied to is now dead and flagged, so I guess I'm not the only one with these opinions.