I haven't read it, but taking what you've said, it's simply a case of "The enemy of my enemy is not my friend".
>but it also compares the medieval church to a totalitarian regime
lel. It's just the kind of modernist eisegetical history that we see now that calls people like John Ball "communist" or our Lord a "socialist" or says that Frederick II of Prussia was a homosexual because he didn't marry. Comparing the Church to a regime like the Soviet Union is actually wishful thinking at best, since it implies that every layer of the Church from the Pope to the parish priest was working on the same "ideological" wavelength when in most cases it just was not true.