I don't think the joke is homophobic; I think it's homoteasing. I'm fine about my sexuality being teased in a silly, jokey, pantomimish, naughty, on the edge, non-aggressive manner.
In short, it's a joke. There's nothing sacred about any kind of sexuality that jokes can't be made about it.
And it's a pantomime joke. The best pantos contain jokes for all ages from young kids to very elderly folk. That's why panto is so great when well done.
I think we need to stop being so precious.