I am surprised anyone even asks that question anymore.The lefties I know no longer argue that he isn't. They just say well it wouldn't matter if he was and you're an intolerant troglodyte for asking.
I have had the privilege of telling unaware conservatives about gay old Barry. It is always an interesting thing. They never say I am wrong.
"Really? How do you know that?"
"Well, when it was announced that he was running for president of the United States the entire gay community in Chicago were outright flabbergasted that he would even attempt such a thing."