This is a pretty weak argument. Using a standard established by an RFC implies a user has read that standard about as much as using Facebook implies a user has read the TOS. The TOS establishes a transitive condition that the user agrees to about as much as they agree to one-to-one commumication under the RFC.

If you have a problem with usage implying consent to a TOS then you can make that argument, but this one is flimsy.