I once saw an elderly man being attacked by 5 people. With my fighting experience, I didn't hesitate to help. He didn't stand a chance against the 6 of us.
Do you think it's right to joke about beating up an old man?
It doesn't matter because no one cares about old people.
That kind of joke is really ageist and disrespectful to elderly people. It isn't right to treat elderly people with contempt, and think it's fine to make fun of them. After all, you'll be old one day too, and I bet you won't want people treating you that way.