Maybe because it makes more sense to criticize actions than belief systems, many of which have profoundly varying styles and degrees of observation. Plenty of folks on the left (and right) criticize oppression, superstition, and the like. Plenty of folks in all camps are guilty of same.
Like Christianity, or any other major religion, adherents of Islam vary massively in how they choose to practice (if at all).
Like Christianity, or any other major religion, adherents of Islam vary massively in how they choose to practice (if at all).