If/when utilitarian calculations spit out a project that compels its various agents to drop their own pursuits and align themselves with it, Williams apparently conceives this as still much a form of ideological oppression as any. Integrity is adhering to one's own position. pursuing one's own projects and convictions --not having one's wholeness impaired by idealized agendas or "impartial POVs".
However, an advocate of a specific doctrine has obviously decided that this is
his/her personal pursuit, even if it required subsuming their "what would be otherwise" ambitions to either its static dictums or methodologically variable prescriptions. Thus, William's all-out appreciation of integrity seems to suggest an eventual tumble into either nobody adhering to a formal, overarching scheme (a world of anarchic or chaotic "do-my-own-thing-ism") or that a vast horde of rival alternatives should co-exist with utilitarianism.