Many consider the idea of "one" God a step backward. Monotheism, it is claimed, is clumsy - it attributes everything to a single fons et origo and then forbids us to examine this resultant "Everything Factory" because it is beyond human comprehension. In other words, monotheism is just another, more pernicious symptom of atheism or agnosticism, except that the believers create a fetishistic idol and then stand in awe of their own ignorance, which it represents.
The Egyptians were not such sticklers about keeping boundaries between monotheism and polytheism. If the Xtians were honest they'd admit that the Trinity is pure polytheism. Indeed, not even the Jews are strictly monotheistic, as their hierarchies of angels indicate, as the Hebrew language itself betrays its polytheistic origins. And as Hakim Bey says, if the muslims understood Islam, they'd worship idols.