What the Fuck. Why did the writers of "Vikings" TV show decide that Muslim's were too honourable for the Vikings to kill?

I know I'm behind on this but I love the show and can't understand why it was fine for three series to kill other pagans and Christians in their churches but then floki sees Moore Muslim's praying in a mosque in Spain. And he and the other Vikings decide that these Muslim's are too passionate holy and honourable that they would die themselves before allowing them to be hurt? What the Fuck is that about? I think I might just stop watching now.