Jokes of this kind are funny because they reference an unstated truth that performer & audience know. They are one of the vehicles by which culture is created. If you think that a joke is communicating a mistruth (by which I mean something disputed, I do not mean a lie) or creating a negative culture - regardless of the intent of the author - it's okay to discuss that.
So in this case, I don't think there's any reason to believe there was an exclusionary intent, and I don't interpret GP as saying that or as calling GGP out, but there may be an exclusionary effect, and I give it's totally reasonable for GP to respectfully add this footnote to mitigate any unintended negative impact.
Some may say this is being a wet blanket or ruining the humor, but people always call you paranoid or a safety Sally or whatever when you try to mitigate unintended harm in any context; you learn to ignore it.
I used to be involved in a biology lab, and people loved to stand on these rickety tables that fell apart at the drop of a hat. So I would bring them a stepladder and politely insist that, if they were in my lab, they were going to use a stepladder. They called me a safety Sally everytime. Doesn't mean I was going to let them smash their heads on the cement floor.
