The enthusiasm for difference sometimes seems not to extend to a range of positions that are assumed to be patently illegitimate. The only thing worse than being right and not knowing it is being right and knowing it absolutely. For pragmatism, as I think of it, one needs to avoid prejudging the prospects for truth, consensus, success, or human betterment in any intellectual or practical endeavor. You try to adopt a sensible approach and then see what happens. At the ground level, as a way of thinking and acting, this means to me a profound agnosticism and modesty about ever knowing if one is on the right track.
Postmodernism is an easy case.
This approach denies metanarratives and universals and, in some of its incarnations at least, denies prescriptivism of any sort. An argument that all philosophers should be postmodernist would be difficult to imagine. Besides, postmodernists need a few modernists around as foils, if only to be able to point to what has gone wrong. And so I conclude that philosophy of any stripe needs difference. It needs difference to generate the friction that yields change.