Yes, there is a logic to PC MC (after all, there can be a logic to various forms of madness...).
Ostensibly, it is predicated on one major factor:
1) Most Muslims Just Wanna Have a Sandwich.
2) We don’t want to “paint with a broad brush” and generalize from the Tiny Minority of Extremists to the vast majority of innocent Muslims around the world.
We see, therefore, a lurking assumption:
3) There is no substantial connection between the Muslims who ostensibly are harmless, and the Muslims actually perpetrating extremist acts.
#3 and #2 are considerably strengthened by a perception that the vast majority of Muslims are a collection of Ethnic Peoples, thus pushing the enormously powerful additional buttons of White Guilt and Respect for Diversity in order to Avoid Being Racist.
4) When anti-Islam analysts and pundits make statements or arguments that threaten #2, the PC MC person is psychologically prompted to go on the defensive. His defensiveness in his mind is immediately transferred to the noble and lofty (and self-righteous and ethically narcissistic) principle of defending the rights and dignity of untold millions of innocent Ethnic People.
This then becomes powerfully augmented when the fear of "another Holocaust" haunts the PC MCs and the Leftists, with Muslims being the "New Jews" forever the potential victims of genocide if we the West go down the road of criticizing Muslims too much (never mind that the problems Muslims themselves generate provoke reasonable criticism of their ideology, if not condemnation and alarm).
Once we see that this is what is really going on, it no longer is a baffling mystery why the PC MCs so doggedly maintain their otherwise irrational position, and why there are so many PC MCs throughout the West -- indeed, as a dominant and mainstream sociocultural fact. And there’s no need to reach for a conspiracy theory about that Dastardly Leftist Cabal of Nefarious Elites to explain this sociopolitically broad and comprehensive Problem of the Problem (the primary Problem being Islam; the Problem of it being the continuing Western myopia to it).