In reality, the EOs and RCs don't "agree" on everything either, they have factions, fractures, disagreements, sects, etc as well.
They may agree on dogmatic doctrines, even though that isn't really true either, but Protestants also agree on "essential doctrines", which we also consider to be dogmatic doctrines which cannot be denied and be legitimately Christian.
So, the false claim of EOs and RCs that Protestants disagree on everything is a dishonest misrepresentation, an intellectual dishonesty that is common to EOs and RCs throughout the history of Christianity.
The EOs and RCs do claim the Protestants disagree on everything, Missey. Where did you get that idea? Please quote.
Yes, I fully agree. If they are not in communion, then whatever they disagree on can't be likened to eating crackers in bed. :) And of course you are right that there are certain core beliefs among Protestants that link us together if only to define what Christianity is. Unfortunately, many claim to be Protestant Christians when their beliefs do not meet even the most basic Biblical standards.