Technically it's the same season as "last season" Its still season 4 as weird as that is. The vikings are a bunch of whores. "Oh you cheated on me, I hope it was enjoyable" wtf? So many love triangles going on right now, no one has the right to be pissed at Ragnar.
The difference for Floki was that the Muslims were worshiping an invisible god to him. The Christians had all there symbols like the golden crucifix and what not. When he saw the Muslims praying, there was no symbols, statues, or emblems. I think it was confusing more than anything else for him. Plus they didn't fight back with an army like the Saxons.