Short version: a pro-abortion dude named Jamie Newman decided to throw out at least one rape threat at Purdue University towards relatives of a pro-life activist there. Pretty brazen stuff: Newman even gave the activist the numbers of cops to call. The police investigated, decided that the threat wasn't credible - but Purdue fairly blatantly signaled that Jamie Newman was a stinking creep who was also now highly radioactive, because after all people who think it's cool to make rape threats as part of a discussion are, well, human scum. As the title above notes, Newman has now resigned (I suggest that he not ask for references).
The 'bitterly' part in the title is due, of course, to the fact that Purdue University had demonstrated the difference between "Alas, we can't do anything about this" and "[Expletive deleted], we can't do anything about this" when it came to dealing with people as foul as Jamie Newman. Newman was clearly expecting Purdue University to issue a pro-forma "We regret any unfortunate remarks but remain committed to our mission to support free expression" and maybe arrange for him to laterally move to another university. What he got was "We would fire this guy in a second if we were allowed to but we literally are not allowed to and we're as aggravated as you are about it." Hence his incredibly unapologetic resignation... because his career was over at Purdue. Newman's life was over at Purdue: the stink from his disfavor would slop onto any academic department, student organization, campus association, and carpool that Jamie Newman still belonged to.
Ain't that a shame? - Spoiler warning: no, that ain't a shame. I understand that Internet trolling is a thing. I also understand that people like Jamie Newman are probably not credible threats: mostly because people like Jamie Newman both would probably soil their pants at the thought of a conflict, and also typically have the muscle tone of asparagus. But we don't need to pretend that we like human scum, even when they avoid prosecution. At least I think that, and so does Purdue University. Jamie Newman clearly has a different opinion, much good it does him...
PS: Some might say that a chill wind may now blow through the halls of Purdue University. After all, it is now clear there that one may not safely attempt to intimidate a person by threatening to rape his relatives. To which I say this: there's an interesting property to chill winds. To wit, it turns out that they're pretty good at preventing things from rotting.
PPS: Notice how this story didn't take off in the national media? That's mostly because progressive feminists are well aware that they're expected to treat progressive men with deference, and give those men every benefit of the doubt. Which sounds a lot like a classic domestic abuse scenario to me, too.