In terms of the thread title, Homosexuality cannot be genetic since a "gay gene" is self-destructive, if we were to evolve to have that gene our species would die out. So either:
a) Miracle
b) Common genetic mutation during pregnancy
c) After birth
A Thesaurus is not a dictionary (For definitions), it means you get similar words. Phobia specifically references irrational fear whilst these all reference an aversion/dislike/distaste towards something.
@Undertaker
Homophobia is an irrational fear of homosexuals or homosexuality
You have not provided a rational basis for disliking/fearing homosexuals
You are homophobic

















But what deems something rational or irrational is the problem here. Using your example of "the human race will die out" is a possibility but unbelievable. Perhaps an irrational fear is only irrational if it is unbelieveable? Using homophobia as an example here is difficult because it is a dodgy subject and seems to be based purely on personal beliefs than any sort of fact, but with spiders the phobia could be justifiable for all kinds of reasons - death, infections or something as simple as their overall design e.g. their weak seeming legs, seemingly useless number of eyes etc. This can cause a irrational fear (e.g. the number of eyes) with something seemingly rational (e.g. weak legs). A friend of mine has a fear of spiders because they find their weaknesses like their thin legs disturbing despite how good they are at killing.