Is religion not important in We're Alive?

[Robzombie]

I love how a simple line of dialogue can seem to have multiple meanings, especially when one puts a LOT of thought into it.

"I didn't fear death, or what might be on the other side if today was my last day. But that was then, this is now."

Fear of a punitive afterlife or 'unlife' as a zombie? Did Michael do something very sinful?
Or just story telling rhetoric?

I think it just means that life for Michael now is not the same as it was. His past experiences in the military and now a zombie apocalypse has probably made him realise that he has to do what has to be done, without any fear of what happens later. He can't be concerned anymore with any thought that he's committing "sin" when he has to look at someone and shoot them in the head. He has no time for that anymore.