Sexuality is something that religions have very restrictive rules about, and anything that doesn't fit within the bounds of those rules is considered immoral. Which is why homosexuals were and still are oppressed, and which is also why pedophiles are oppressed essentially just like homosexuals once were. Being a pedophile is widely considered to be a moral failing, just like homosexuality once was (and by some still is). This taboo leads to people not rationally looking at the actual facts of the situation, not considering the actual consequences of what is happening, instead anything that is in any way associated with pedophilia is seen as equally objectionable, which in turn leads to a general lack of distinction.

"Child porn" is just a generic label for "terrible immoral stuff done by immoral people involving the idea of sexual practices involving children" in the public discourse, and a terrible label at that, given that it either tries to use a negative view of pornography to evoke an emotional reaction to an essentially unrelated topic, or trivializes the experience of abuse victims whose agony is documented by suggesting that it's in some way similar to consenting adults producing erotic works for the pleasure of other consenting adults to look at. It's a bit like using the label "child horror movies" for snuff videos depicting children.