Bully: Ur Gay.
Me: I'M STRAIGHTER THAN THE LINE IN OSAMA BIN LADIN'S PLAN.
Bully: *runs away and hears crash*
Listen up, buttercup. The joke is that the dude is saying he's super straight, like the line in Osama bin Laden's plan. Get it? Osama bin Laden, like, the guy who did 9/11? So the straight line refers to how straight the planes flew into the towers. That is what happens when you skip history class, dingus.