There seems to be no specific link between autism and sexuality. However, people with autism are more likely to discuss their sexuality on websites like this, because their identities will be hidden, and they're less likely to be persecuted by the more closeted and clueless people of a more neurotypical mind-set.
Gay-bashing is forbidden here, with gay-bashers getting themselves banned quickly, so this might also play into the comfort level that gay autistic people may have on this website.
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The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.