I know many non-Muslim people that say "As-salamu alaykum." It translates to "peace be upon you." It is a traditional Arabic greeting, has nothing to do with religion, and was totally appropriate for Obama to say to a room full of Arabic speaking diplomats.
When he says "I am one of them", he is saying he is an American, not that he is a Muslim. The propagandist is once again using tiny excerpts of a speech, and using it out of context.
Why is this video so chopped up? Why is it so heavily edited? Why is the propagandist that made this afraid to use Obama's statements in their entirety?
It is revealing to see what kind of propaganda the alt-right is putting together to play on your racism and xenophobia these days. It makes me sad that such deceptive material is being fabricated, and that people are too afraid of what they don't understand not to see this heavily edited propaganda for what it is.