Why do people say, “Call it pedophilia, not childlove” when the word “pedophilia” is Greek for “childlove”?

Just because two words have identical semantics, does not mean they have identical connotations.

Pedophilia in modern society has extremely negative connotations. It didn’t have negative connotations when it was coined in Ancient Greece, because it was coined under different cultural norms. Words carry with them the connotations that a culture puts on them.

Advocates seeking to avoid those negative connotations may try to do so by coining a new word, which doesn’t have those connotations. Calquing the word into English “childlove” is such a strategy; “childlove”, being a new coining, doesn’t particulary have any connotations, and “child” and “love” on their own sound nice. “Call it pedophilia, not childlove” expresses objection to the strategy, and wants to keep the negative connotations in place.

Literal meaning is only one part of the meaning of words.