What's with the lithp?

My personal experience suggests that lisping, as a linguistic and natural phenomenon, as opposed to artificial (used in isolation in a speech act) or medical lisping (sigmatism), is virtually inexistent in my native language, but we have other mannerisms that are seen under the same light by general society. If I said that, at the moment, I know what’s psychology’s general view on its causes, I would be lying. For a technical and reliable answer, I would recommend searching in google scholar. That said, if I had to guess, I would guess it’s a mostly cultural sociolinguistic phenomenon, but I may well be wrong

Sometimes one can guess, but intuition is quite often misleading, and its efficiency can be dependent on the community (or individual) in question. Lisping and other mannerisms are present in the behavior of some homosexual men, but also in that of so called “metrosexual” men, not all of which are homosexual, and even in people that do not belong to either of those groups. There are also lots of homosexual people that do not use any of the mannerisms generally associated with them. My best friend is a homosexual man himself, but no one would guess that from his behavior. Which does not mean such mannerisms do not exist, nor that they are not more common in some communities than in others (though I would not know; I haven’t read the correlational data on them).

Have you ever MET a gay person? Find me a clip of a single one with a lisp.

No lie.
I have never once met a gay person with a lisp.

Not to say I haven't met some with an effeminate way of speaking, but this idea that 1. it's a lisp, and 2. that many have one has always been crazy to me.

Tons of caricatures have the "Gays don't lisp they just pronounce their "S's" thing" (Even if it is a gay actor "dialing it up") but I have yet to meet an actual gay person, or see one in a real interview or discussion, who has it.