Why is it "controversial" to have a left leaning government and a significant population of Christians or Muslims? Yes, Kerala had early "true" communism (land reforms, nokku kooli) but since then it has just been a left leaning, liberal government. Also answer why you find it controversial for it to have other religions than Hinduism.
It's politically charged to have politically-driven narratives on HN, especially when it has the basis of ethnic politics. This makes it controversial in the first place.