"The key difference between science and morality is that science is generally falsifiable. I believe evolution because I can find fossils that support it. I believe relativity because it predicts the orbit of mercury and gravitational lending better than any other competing theory. I can also discard ideas if I find contrary evidence."

But for somebody who doesn't understand evidence for evolution it doesn't make a difference. What makes you so sure that it isn't the same with morality? Somebody who doesn't understand science can think that there is scientific evidence for creationism.

"Morality on the other hand isn't falsifiable. I believe murder is wrong, but have no objective evidence to back it up. Theft is wrong, but it can't put together an objective argument based on external evidence short of "stealing screws someone over and I wouldn't like it if someone stole from me"."

It isn't about you, stealing can be objectively bad for somebody, and what you think about it doesn't change it. Also for example historical evidence isn't falsifiable either but you accept some of it.

"Having said that cultures can all agree that certain actions are morally just or unjust, but in the end it's the culture that decides and cultures could easily decide the other way. Look for example at the Crusades. Each side thought they were morally justified in waging war and killing the opponents..."

I am utilitarian to me utilitarianism is true even if every other person in the world would disagree, and they would think that somebody else is moral, to me that would mean that everybody else is mistaken. I don't think that morality has anything to do with culture, or with what people think.