A religion teaching us to kill or hurt animals => it can't be true/be the Will of a Good Creator.

That's nice!!!
But please remember it can never be good to take the life of an animal - including "kosher animals", like tuna. They are sentient and are suffering when people are killing them.
It is not ethical to take the life of another sentient being (which always causes suffering, and is completely unnecessary) or to cause him/her suffering in any other way - regardless of what any religion tells you:
http://www.youtube.com/watch?v=uQCe4qEexjc

Please read : www.worldpeacediet.org