Joker has always previously been portrayed as straight. Were you offended by his actions for the last 60 years ?
I don't think his love of Batman is sexual. It's more like worship or a man-crush. Not to mention that he wants to marry Batgirl in her title currently. Unless she's his Bat-Beard
That is a form of psychological torture he is applying to her. He does not expect this relationship to progress anywhere. As you can infer by the fact that he shot her in the fucking spine.
Has been portrayed as straight. Past tense. Has been suggested to be straight mainly due to the prescence of Harley Quinn. What was it he said about her in the arc? Oh right.
"When did I ever say I found you beautiful?"
As for not being sexual,
"Hello, darling!" (First fucking words he says to Batman).
"What, no hugs? No kiss?" (the next freaking line)
"You remembered! That is how we did it last time. Back when we were full of vim and vigor! Two younguns!"
"You're nothing to me but a maniac."
"Shh. Don't do that. Don't pretend. Not to me, your faithful court jester"
"I even know which soap you each use in the shower (and why you always smell so good, Nightwing)."
This isn't some kind of subtext, this is a neon sign flashing over every page.
Whether Joker actually is gay or not is completely irrelevant, as he is either invoking the idea that homosexuality is abhorrent and revolting - if he's actually gay, the writer is trying to suggest it and use it. If he's not really gay but doing it to freak out Batman (which is stupid cause it contradicts what he says to Harley in private), then he's doing it cause he knows it will freak out Batman more. Which means Batman is homophobic.