I don't think that implying someone sucks weiners means that also implies someone is gay. You can chow down on some dong and fly straight as an arrow.
And that's really not even the intent behind the joke. He implied that Donny sucks Putin's Russian Polish sausage not to imply that he's gay, but, again, to imply that he's Putin's bitch boi.
It was used in this context: "Why did Randy get a promotion?"
"Oh, because he's gobbling the boss's gonads."
It's interchangeable with calling someone a brown noser, or a suck up.