I think it’s mostly *because* jokes are subjective that they can be offensive. Pay attention to who the object of jokes usually are and who is doing the telling. Could you replace the object of the joke with “a middle-aged white guy” and still have it be funny? Does the joke rely on shaming or demeaning the object to make its punchline? Does it rely on implied “otherness” of the object, or implied superiority of the teller?
Often the tellers of such jokes will dismiss the harm as “I didn’t mean anything by it.” But if there is an imbalance of power, the harm gets done anyway. Same with teasing — it isn’t funny if the person on the receiving end is lower in the power structure than the person dishing it out, especially if it happens in front of peers or supervisors. Over time, this kind of “humor” subtly undermines the perception of competence of the person joked about.
