I could not remember seeing Alexander talk about his sexuality, and all I recall was somebody in r/ssc complaining that we didn't know he was anhedonic (which is weird, as I found him talk about his sexual feelings, like the poster didn't get what asexuality means (unless he talked about this more and I missed it)). But I looked it up, and I found this:

"Applying enough charity to fully fund the Red Cross for the next fifty years, [name of neo-nazi pickupartist removed] seems to be saying something along the lines of “Polyamory is especially well-suited for asexual people”. And I agree!

Many of the people I know in successful polyamorous relationships are sexual, sometimes even highly sexual. But I also know a disproportionate number of asexual polyamorous people – including myself – and the combination seems to work really, really well."

Source: https://slatestarcodex.com/2014/09/27/cuddle-culture/

So yeah, his sexual superiority comes from being an ace poly person I guess (not sure where you got that from his writings, but whatever. Do wonder why he feels the need to interact with (at least intellectually) and link to people who want him to stop existing for several reasons whoever, esp as this is not really extended towards the left (and for the record I don't want him to stop existing)).