Optional GCSE RE should be completely decoupled from the compulsory RE provision which should be scrapped and replaced with philosophy & ethics.
Phil & ethics should teach a universal secular morality which will support a cohesive sceptical society able to think for themselves and have a common foundation in what is right and wrong.
The problem with the current RE curriculum is that it teachs a historical fantasy of religion that bares very little relation to how muslims/christians/jews actually live here and now.
So if we teach children that all religion is valid, that we should accept everyones views and never offend them, how can we complain when some children take their religion literally and try to enforce it on others? We need to be more honest.
It really annoys me when RE teachers teach what athiests believe in. Athiests do not have a belief system, they do NOT believe their is no god. The only assertion an "athiest" makes is that there is no sensible reason to think that theists are right.
My DS spent an RE lesson on the pros and cons of ISIS, really a whole lesson on what's good about a murderous death cult just to get balance. Maddness.
Also my DS wanted to op out of RE, school said no, its compulsory and we don't have any provision for kids to do anything else. I would have taken it further but my son was so worried about being singled out that we just accepted it. That is forcing religion on children.