He was Jewish by blood and agnostic AFAIK
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most likely, the nazis hunted him and he only just escaped, and all his library was burned
not just a jew but deeply opposed to, and vocal about his opposition, and very clear in his reasoning, why he was opposed to socialism
indeed, from the superficial reading, both christianity and islam's main texts seem to open up the potential for corrupting both religions with socialist ideas, though like you say, the muslims are probably more proof against it, in the West christianity has basically been coopted, the 70s and 80s with the thatchers and reagans saw to it that the public image of christianity was thoroughly tainted
this kind of false piety is used by power to break the social cohesion enabled by these religions, it's tragic...
personally, i always hated atheism, when i was off the path my thing was ... idk exactly... ontological anarchy, psychedelic illumination, taoism... part of my road back to Christ had to do with reading the Qur'an where it talks about how there can only be one God because many would annihilate the universe