People, whether they’re neurotypical, Asperger or whatever, get turned on by a whole load of different things. Some like people of the opposite sex. Some like people of the same sex. Some are more aroused by ‘bits’ of people (legs, feet, whatever),inanimate objects or fantasy situations. This is all just part of the wacky mix that is human sexuality. If it’s not harmful to the person having the fantasy, or to anyone else, and if it’s not illegal or dangerous, then what someone is thinking or doing when they’re alone in their room is their own business.
Wendy Lawson has written a really good book called ‘Sex,Sexuality and the Autism Spectrum’which some people have found very helpful as an ‘insider’s guide’ to the topic of Aspergers and sexuality. A link to the page on amazon – which includes details about the contents – is
Hope this helps.