What about Buddhism?
I studied various religions before becoming Muslim, but while having a Christian upbringing I obviously studied Christianity in depth first. As such I studied Hinduism, Jainism, Sikhism, Buddhism, Shinto as far as far eastern religions go, etc...
Buddhism? An impractical man made religion ultimately riddled with contradictions. Also denies God (saying it doesn't matter whether God exists or doesn't exist is pretty arrogant) and then there's the worship of an idol of Buddha, which makes little sense. They will say they are not idol worshippers, but then alot of things 'appear' and don't 'appear' what they are, everything is a riddle. I don't buy into it. Renouncing desires? Yet there is the need to have a desire to be good, amongst other things too. Desires should be channelled properly not just denied but understood why.
In a nutshell what Buddha himself preached seemed overall good, his journey, and revelation as a prince coming out, was all interesting. However what 'Buddhism' is today, is non-sense to me.
As a Muslim today, I don't find it hard to speculate that Buddha himself was a prophet of God who saw what was going on around him, experiencing life as a prince, then outside and trying to ascertain the truth in his life through his journey. Naturally what happens afterwards, people can pervert the message and teachings, erase and add what they want. Hence an idol of Buddha makes very little sense when he said no such thing. It's also funny that they will say well we are not actually idol worshippers, but then in it is a religion of a lot of contradictions.
