It is a difficult situation. Sex is more than just about the physical act as it does induce strong emotions and feelings.
With an IQ of 48 he probably is lacking the emotional capacity to understand the emotions and appropriateness. However how can you ban someone from having sex?
Quite rightly he probably would be a danger to himself and others in terms of not understanding the need for safe sex. It seems he was in a relationship but I can also understand why they would worry that he could be taken advantage of.
A complicated situation indeed and I would need to have more information to make a true judgement.
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