Exactly, but its understandable why people would get offended by jokes about suicide, abuse, racism and so on. They may have experienced these and when people joke and mock those topics they will be hurt by those jokes. It all comes down to whether or not you care about strangers feelings, telling a joke like that doesn't make you a bad person but if you went up to a rape victim and you knew they were a rape victim and still told a rape joke to hurt them deeply, it does mean your a jerk. (Obviously)
I just want to comment on the bolded part. You don't have to be *trying* to hurt them deeply to be a jerk in this instance. You don't even actually have to know they've been raped, or anything about them. If the person you're talking to starts looking distressed/upset/shocked/horrified or anything else that a normal, rational human being would be able to recognise as a cue to *stop talking now* and you notice it and identify the non verbal signal correctly BUT YOU KEEP TALKING to finish your joke - then you are being a jerk right now. Putting your own feelings and wants ahead of those of the person you're talking to, and doing so whilst aware it is upsetting them, is unescapably selfish and jerkish behaviour.
Communication is a two way street : to be understood you need to communicate your meaning and intentions effectively AND they have to be received and interpreted correctly by the recipient. And vice versa. If the person you're talking to isn't supposed to react to you in any way except to lap up what you're offering then you have NO business talking to them - you don't want to communicate, you want a passive and captive audience.
I have a quite dark and biting sense of humour and i can be scathing and brutal in my choice of words - knowing this about myself doesn't give me a free pass to say what I please without consequence. If I offer a cutting rebuttal to my manager in my workplace, it may be technically hilarious to an observer but even if my manager is privately amused, I'll still get a (deserved) talking-to.
If I'm sharing a funny story about one of the children at work with a random person at a social gathering and they suddenly start looking upset at what I'm saying I would be a jerk to continue as though nothing was wrong. Whether their reaction is from trauma or something *I* think is serious or not - if they're upset, and I continue, I'm a jerk. Yes, this has happened a few times now. Once was because it was the anniversary of their stillborn baby that day. Another time a word I said triggered a traumatic memory for them. One incident involved a stranger telling me off for allowing children in my care to play in a shallow river with me - once they stopped and listened to me, they understood they'd jumped to a highly inaccurate conclusion because of something they'd read in the news, which they apologised for and we kept chatting.
I'm not "politically correct" because of any need to fit in or look good. I'm considerate of the feelings, thoughts, and reactions of others because I'm, frankly, not a jerk. When I make mistakes, I acknowledge them. I apologise, explain what happened from my perspective if relevant, and take care to try and understand the other person's perspective. I may not agree with it, their values are often not mine - but just as I expect a certain level of politeness and curtesy, so I try my best to give that to the people around me.