While a lisp would not in and of itself be "evidence" of a person's homosexuality, there is undeniably a "gay accent" that has its own phonological features. This is backed up by impartial linguistic research as being an adopted feature
, in the sense that it can be and is turned "up" or "down", depending on the social context of the utterance (see Podesva 2011 for one such study).
As for Amharic, it is spoken much further "forward" in the mouth than English usually is, making it sound more lispy than English (and, by contrast, English sounds funny to Amharas, like we're speaking with our tongues stuck in our throats). Spanish, particularly Peninsular (European) Spanish, has the same phenomenon going on. It's kind of hard for a Spanish guy to sound tough with all that "essss"-ing and "ossss"-ing, and certain other Spanish-speaking people (e.g., Argentinians) are mocked by others for having that feature that makes them sound like "wannabe Europeans".
Hmmm...why not forget about your suspicions and any rumors you've heard and study some sociophonetics?
That ought to calm you, somewhat. For the rest, just pray.