Did you miss the point?
I think you did.
Its not about what its OK to be offended about: its that THREATS of EXTREME VIOLENCE are not okay.
It is quite possible to define a set of rules that do not include committing violence, particularly here, sexual violence, against someone. If you can't get behind that, you're part of the problem.
This isn't about made up offense and political correctness and differing cultural norms. We're talking about threats of rape and extreme violence here. Its not okay to threaten to rape someone. Its not okay to threaten to murder someone. The topic is not a joke. You're the problem if you think otherwise.