I'll put this one into the "control and direct" column. Teach him time, place, and context. Because his searches could lead him to places on the internet not meant for youngsters, set a rule that you MUST be helping him if he's going to search on the internet. In fact, that is probably a good rule, period. My 10 year old daughter still has to ask permission before she googles anything - she just has no idea what terms might take her places she really does not want to go.
All parents get tested on learning how to let go of assumptions and discomfort with certain taboos, but I think us parents to AS kids get that lesson in spades.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).