The criticism I hear from Whell or read in this
link has to do with the semantic use of the word "contract." Somehow, the criticism seems to use the legal meaning of "contract" as a trump card to invalidate the notion of a "social contract."
Isn't that kinda like saying that you need to give a rabies shot to a hot dog?
As a German speaker, I'm quite familiar with compound words and am able to recognize that "social contract" is a compound word used to explain a concept that differs materially from "contract" used in a purely legal context.