First? Listen to the following (it's video, but you don't really need to watch--listening is good enough).
(thanks to Night Serf for finding this)
The top comment:
3 weeks ago
Religious people do not get their morality from an objective source, because if they did:
1. Believers in the same religion would not disagree with each other concerning moral propositions.
2. Believers would not pick and choose which beliefs in their holy books they would follow and which ones they would discard - which ALL OF THEM DO. The fact that they are selective in choosing what moral teachings to subscribe to shows that they are using a source of morality OUTSIDE their scriptures.﻿