But it's okay if you're passively shielding abusers? I mean that's the crux of the argument here. "Sure, we're the preferred tool for child abusers and sex trafficking but a few bad actors don't invalidate the need for private communications" is an argument I would accept as a technologist but doesn't seem to fly with the public. It doesn't mean that E2EE is DoA it just means that you can't just throw up your hands and say that doing something is impossible.

Have the client check the FBI's CP database and refuse to send pictures that match. Sure it's open source and abusers could recompile it but they wont. In the same way that blocking the default curl useragent stops 99% of spam at my company. Would be attackers could change it, but they don't.