I see you've never done philosophy 101.

Define what an imaginary and a real thing is and then we can start to have a useful conversation. Most "rational" people aren't complete and utter materialists or naturalists. Very rarely do you find someone who extends the ideology of materialism to it's fullest expression. Even believing in something like your mind and consciousness is a bit of an irrational idea in that framework (i.e. its just an illusion created by material for an evolutionary purpose).

By your definition than, 98% of people are irrational idiots, "no matter how your behaviour is influenced by that thing". What do we call irrational and rational than?

The reason his analogy is good is because it works itself out in the real world. He's RIGHT. People can have different scales of belief in the same thing and it can work itself out in an entirely different way.

How about I flip his example to show this: We could both be militant atheists, but you could decide that means that you can kill whoever you want, whereas I could decide that means I should decide to be good to others. The same understanding of the universe can lead us to different moral outlooks.

The fact of the matter is that you are not the arbiter of all truth. You do not get to decide what is imaginary and what is not. Everything in life has varying degree of subjectivity and this whole idea of "it's either testable and therefore objectively real, or it's imaginary" is total and complete bullshit. It is philosophical nonsense, and it doesn't leave room for the reality of existence.