There's a difference between showing children that religions exist and what the central tenets of those religions, it's cultural roots and teaching the tenets of a single religion as if it were correct or factual. For example, teaching about slavery does not condone slavery nor produce slave traders. RE, if it's included in a curriculum should also include atheism.
Potentially we are on a slippery slope because once weight is given to teaching the 3 Abrahamic religions with regard to the children making up their own minds then one must then be obliged to teach about every faith ever recorded including things such as Scientology. How can one become a follower of Shinto unless one has heard of it?
Secondly the same goes for teaching creationism in science. Which versions from which religions are you going to teach in science classes? Thirdly, it's not science, because it's not testable. Fourthly teaching the "controversy" would be like teaching that the flat-earthers have a point and that there is equal validity between round-earth and flat-earth theories. There is only controversy in the minds of the uneducated or the wilfully ignorant.
Religion should not get a free pass, it shouldn't be treated with kid gloves or given respect that it doesn't deserve.