The phrase "to believe this stuff" means that someone trusts or accepts the information or ideas being presented, even if others might find it questionable or hard to believe. Full definition
Well we should find out who actually believes this stuff and have them give us their material possessions since they aren't going to need them obviously. (religion.blogs.cnn.com)
If you want to vote for someone to represent you who believes this stuff, it's your problem, not mine. (religion.blogs.cnn.com)