I've heard arguments in favour of this level of surveillance going a bit like;

"I have nothing to hide and I think this is a serious problem, so I'm okay with the EU scanning my messages if it helps fight CSAM"

And if you argue against in case of wanting privacy the counter-argument ends up being; "Do you think CSAM isn't a problem or you're on the side of the pedos?"

Don't see how to argue with a person who simply doesn't care about the right to privacy or these regulations being the first step to mass surveillance. I.e. like someone wrote "Four Horsemen of the Infocalypse"