I think a joke's intent is something that can be argued about forever, especially in a courtroom / legal situation.
You can never really know - just being ironic or edgy would carry no bad intent, but then again, people can be assholes on purpose with their "jokes" too.
I am also really not a fan of the "if one person claims to be offended, then it is offensive and punishable" approach either - for a different version of the same problem. One person's negative opinion could be motivated by their own overly defensive personality (i.e. assuming bad intent where none exists, having no sense of humour). Or even worse, perhaps the complainant is a dishonest person who realizes that in this current culture, all grievances can be weaponized regardless of merit, and that gives them enormous power - they get an opportunity to promote themselves by getting rid of the other person or by collecting sympathy as the "victim". So the "accusation is all you need, not proof" model just leads to a different kind of abuse.
TL;DR: some people just enjoy being jerks; others are always butthurt about small things, or just pretend to be as a social weapon.
Yes, both of these things happen in real life; I have seen both. Human nature is problematic - nobody has yet invented a foolproof "asshole detector" to get these judgement calls right every time.
