Archer was no racist. He had serious and totally justified problems with the ways the pre-enlightenment Vulcans behaved and he didn't hold them back. So you could claim that he wasn't politically correct and I think this lack of diplomatic skills was a liability in many cases but not when dealing with the Vulcans.
Let's not forget that the most sublime friendship in ENT was anything but politically correct. Archer and Shran never held anything back which is precisely why they became friends.