I have no issues with anyone’s belief in any deity, assuming it brings no harm to others
Do you know of any seriously-believed-in deity or religion that meets that requirement?
Nope. Even the pacifist ones induce people to let themselves be stomped all over by the bad guys. Which in many ways is just as bad as the ones that tell people to kill in the name of their god.
An equal concern these days is the 'Green' ethos, which contains many of the attributes of a religion. Some of the comments by these guys, such as that the human race is a blight on 'Gaia' and ought to be exterminated, really make you a bit concerned about them spreading this stuff to the public. Not to mention the scams. Homeopathy, a million crazy effects of climate change, you name it. This stuff does harm to others because it makes energy very costly which is very hard on the poor, and induces people to stop taking medication which would otherwise cure their illnesses.
The litmus test for a religion is if you are immediately labelled a heretic if you point out an inconsistency in it.