Passion

what I don't understand is how they can be so convicted and passionate about something that is not real.
If they are so moved by a deity that is not, could we also be equally assured and emotional about a deity that is not?
I just don't understand how Muslims can appear equally as commited to Allah as we are to Jesus, but only one is true.

I guess I am thinking about it a lot because I am reading so much about the middle east and Islam.

The only explanation i come up with is the "Religion is an opiate for the masses" kind of thing and that isn't very comforting to my beliefs.

There has to be some explanation of how both groups can feel equally convicted. I mean, maybe Satan can evoke such feelings to and masquerade as other gods, but then, what if Satan has deluded the Christians and it is really another religion that is true?
We can say "they are the ones that have been decieved", but they say the same thing about us! It's kinda scary
Faith... blah. why can't we have proof?