There may be good arguments for allowing these types of "features" but this is not one of them. I'm so tired of seeing "it's fine because everyone else is doing it too"
Like mentioned elsewhere in this thread, the problem isn't the presence of these types of components, but how opaque to the user (read: highly technical user) they are. Also they exist because there is demand for their features.
The talk I linked makes the case that OS development is failing by pretending these co-processors are outside its scope, and hardware vendors just go and do their own thing on the side. I add that this incentivizes proprietary firmware instead of open one. I mean, if there were pressure (from paying customers) for Intel to support open-source IME firmware, they'd do it. After all, they just want to sell more chips.