Van Jones laughs, riffing on the "come out" language in the question: "Do you think President Obama would lose some of the black vote if in fact he did come out in support of gay marriage."
Let's analyze why Van Jones thinks that's so funny. The foundation of the joke is the assumption that black people have negative feelings toward gay people. It works as funny because only because we're expected not to take this negativity seriously — either because black bigotry doesn't matter — or is fair retribution for America's racism — or because gay people don't matter... or all three. Throw in the breezy assumption that black people, looking at Obama, will not in any way engage with the actual political issues. Jones portrays black people as emotional, simple-minded, and all alike.
It's a big stew of racial stereotypes from the lawyer/civil rights activist who was chosen by President Obama as the first Special Advisor for Green Jobs, Enterprise and Innovation at the White House Council on Environmental Quality.
Are we supposed to laugh?