Has nothing to do with homosexuality and homosexuals being portrayed as some sort of perversion, in a similar league as I don't know...a rapist.

With respect, I don't believe it does anything of the sort. It isn't a joke about ALL gay people. Its a joke about a single gay person, just like there are thousands of jokes about Scottish, English, Irish, Polish, black, white, disabled, blind, deaf, old, men or women.

Now rape, rape isn't funny. Even slightly.

Murder isn't funny, but there are lots of jokes that end with someone's death. This is often rated as one of the funniest jokes:

A couple of hunters are out in the woods when one of them falls to the ground. He doesn't seem to be breathing, his eyes are rolled back in his head. The other guy whips out his cell phone and calls the emergency services. He gasps to the operator: "My friend is dead! What can I do?" The operator, in a calm soothing voice says: "Just take it easy. I can help. First, let's make sure he's dead." There is a silence, then a shot is heard. The guy's voice comes back on the line. He says: "OK, now what?"

Is that joke not funny? Should it not be told in case it offends someone who lost a family member to a shooting?

Lastly, what kind of representation and what kind of leadership can be expected from a man whose heights of humour involve taking advantage of the least fortunate,

Again, I completely disagree with you on this point. He isn't attacking any particular group it is just a joke.