I don’t think this guy murdered all those people for their religious beliefs as he wasn’t particularly religious himself. He just didn’t want his nation infiltrated by a people who’s political doctrine is to kill anyone who isn’t a muslim....and who have clearly stated their intentions are to change nations political systems to their laws.
No western nation has or ever will assimilate its muslims.
Since republics depend on some commonality in religion and traditions, the seeding of muzzies around our nation is clear intent to destroy the US.