In honor of my birthday, Glen Whitman debunks the dependence of morality on the existence of God as follows: "Well, um, I’m an atheist, and I think it’s wrong to kill people and stuff. So there."
Along the same lines, I can show that the fact that people do not float off the earth and into space does not depend on gravity: "Well, um, I don't believe in gravity, and I don't float out into space. So there."
See, philosophy is easy, if you just don't give a crap what sort of argument you use!