One of Pikachu's repeated canards is that the ancients were always making "new religions" out of "old parts" -- and this is a canard used repeatedly to infer that Christianity ought to have been no different. Aside from the core begged question of what was borrowed and if it was, his canard is in fact a semantic disgrace. Yes, there was a great deal of "tolerance" of other religions -- in fact, it was the inevitable result of polytheism: You'd want to be sure you didn't offend any god that existed, so you'd honor all of them. It makes sense given the world they lived in. That's the real reason why there was no such thing as "right doctrine"...outside, we may point out, certain religions (like Judaism!).

Syncretism? Not exactly. Pikachu avers that ancient religions borrowed and adapted from each other. In a sense that is correct. But it's not quite the same as his "they built new religions from old parts" bologna sandwich that he keeps making. A better description would be: They took old parts and attached them to other old parts. They did not create a "new" religion; they added on to an old one with other old ones. And that won't work with Christianity as an explanation, because that was not a case of one "old" meeting another (unless you want to claim Judaism met paganism, which is not what Pikachu argues).

The example of Alexander in the Middle East equating his Greek Gods with the Middle Eastern Gods is an example of this. This is not Alexander "borrowing" but adapting. Same with the Romans and the Greek gods. It was figured that i.e., Zeus in his Roman form (Jupiter) must have asked people in other areas to worship him in a different way, for whatever reason, so it was all combined. It wasn't "new" any more than you get a "new" recipe for Chocolate Corned Beef Cake by combining two old ones for Chocolate Cake and Corned Beef. What you actually get is, at worst, a mess. But nothing "new".

So then. So much for Pikachu's case against Christianity. Unless he wants to switch gears, his whole "new religions were built from old parts" canard just suffered a fatal reality attack.