No, if one person gets the joke, it doesn't matter if anyone else understands it. I mean, usually when jokes offend, or maybe dont make sense, it's not worth the effort to find out. I will defend comedy whether it offends me or not.
Who''s offended? I'll defend comedy, too. But just calling something a joke doesn't make it one. It was a poor attempt at a joke, if that's really what it was.
I'm giving the person who made it the benefit of the doubt that they're an adult. Obviously, if they're a small child this would be moot.