Semantics aside, whether or not FB users are "customers," FB obviously needs them in order to be in business. Without them, it gets 0 dollars.
So the original point, "you have no right to complain because you don't pay to use it," is silly. Whether or not users have a RIGHT to complain, FB should prefer responding to their complaints over losing them as users.
As it happens, it seems that most FB users aren't phased by anything FB does in terms of privacy or heavy-handed policies. So unless those complaints get loud enough to signal that users are about to start leaving en masse, FB doesn't need to care.