>While not referencing the joking relationship specifically, Žižek argues it allows us to frankly acknowledge problems, giving people the opportunity to perhaps work through them.
That is the key though and many people ignore it. Being offensive comes with a price. We need to make sure we are buying something with that price or else we are wasting our social capital. Offensive jokes that exist for no other purpose than to be offensive are therefore bad. Offensive jokes that are working towards exposing or furthering the discourse on some problem are still worthwhile. Many people can't tell the difference between those two.
1. It absolutely doesn't apply to the case of person A telling person B a joke about person C (or the category to which C belongs), while A and B are not in that category and C is not in an apriori "joking relationship" with them.
2. It is not so difficult for someone from a privileged group to basically decide unilaterally they are in a "joking relationship" with someone else, who is forced into being the butt of jokes.
... and I would say these context are where the offensive jokes are "really" offensive. However, Zizek's point about such jokes allowing issues to surface may still be valid even in this situation.
That is the key though and many people ignore it. Being offensive comes with a price. We need to make sure we are buying something with that price or else we are wasting our social capital. Offensive jokes that exist for no other purpose than to be offensive are therefore bad. Offensive jokes that are working towards exposing or furthering the discourse on some problem are still worthwhile. Many people can't tell the difference between those two.