I haven't followed or read any of those threads except for a couple of posts in the link JUPITERASC provided.
There is an Astrological 'Part' that is titled, the "Part of Homosexuality'', it's also known by the title, the "Part of Surprise". I haven't worked with the 'Part' before, not much anyways. I have only calculated that "Part" for about a dozen charts...those charts that I ascertained all the Parts that use the Asc. as the "Personal Point" [the Personal Point is the first factor in anyone of the Arabic/Astrological Parts' formulae ["Personal Point" + "Significator" - "Trigger"] It is a more modern "Part" in that it has Uranus [a 'Trans-Saturnian' Planet] as the "Trigger". Asc + Mars - Uranus. Though I seriously doubt that it is some sort of clear indicator. Most likely it comes up aspected in some way or another on the chart of many Homosexuals and thus got the reputation.
There are all sorts of aspects and such that give tendencies towards sexual preferences a bit "off the well beaten path" [pun not intended...but I might just use that sometime.]. I am in the middle of writing a thread on Bill Clinton in the Mundane forum and the Monica affair has really shown up in Bills astrology, or what I believe shows a good cause for it or contributing to it. Bill also has a Mars-Neptune conj. by a very tight orb and they in turn are both conj. Venus about 7* away. All were in Libra at birth...his Asc. and Venus had progressed to Scorpio just at the time of the affair and just before the affair began [or right at the onset,] Bill's natal Asc. had progressed to the 17th of Scorpio which happens to be the Part of the Libido [Asc. + Pluto - Venus] for the natal chart of the USA [zero hour July 4, 1776 chart] ...then it progressed to the next degree about 2 weeks before the 'affair' ended.
btw...my asc is @ 17*
10' and if I was born some 30 to 40 seconds early than is recorded it might be in the previous degree...the same as that Part of Libido.
So, you might want to take a look at that Part also.
Here's a little music to accompany your search for the answer....
http://www.youtube.com/watch?v=idhxrZKlLvc