Nigga, people have already proven that Intel ME can skim damn near everything you're doing, and send it off/secure it/ store it in such a way that you literally have no idea, or way to even know it's doing it.
Apple allowing a proprietary processor, of which we would know zero of it's capabilities, intercept keyboard, mouse, video, audio, and more would be 100% questionable.
If I told you "Hey, user, here's a device you can plug into the PCI-E port of your desktop that'll make it faster!" And you knew nothing of what it was actually doing, actually responsible for, or actually capable of, beyond that it requires drivers with access to nearly everything and is clearly capable of it's own networking/processing/storage, would you accept? 99.9% would say absolutely not. They would have no idea if it's skimming credit cards, stealing identities, remotely launching attacks on state enemies for foreign nations, or what. They would want no part of it.
Now, I don't think Apple wants your credit card to commit fraud with, but the idea that Apple can, just by you "agreeing" to purchase the "2018 Macbook Pro" gather information such as: keyboard usage information, network metadata, encryption key information, and system metadata, they could resell it, use it themselves, or it could be stored and leaked and used maliciously. Hell, it could be called into use by state bodies. What you type, when you send network information, network information, SSL certifications and more could all be gathered and used against you, against others, and all just because you thought that having a mystery chip in your Macbook Pro was a great idea!