If even 95% of males are heterosexual, those who would ban homosexuality as unnatural need to answer this evo psych question: why are 5% of males not heterosexual? Evolution tends towardss great efficiency.

Yeah, you probably need to read more books on evolutionary biology. While technically correct the latter sentence is a misleading generalization when thinking about certain traits. I recommend you start by familiarizing yourself with genetic load to see an example of how evolution can end up relatively inefficient at doing some things. Also note the role of path dependence in the natural world.

We don't have a 5% blindness rate or deafness rate.

A noisy figure, we have estimates going from 1% to about 6% for all non-heterosexual people depending on country and methodology. Statistics vary but about 2% of men are totally infertile. We also have infectious diseases and parasite infection rates for some organisms above 5% in human populations that get in the way of spreading genes as much as homosexuality. This is considered a plausible explanation too:

A related hypothesis is that the proximal cause of homosexuality must be an infection. Cochran does not suggest that an infectious agent that causes homosexuality is spread by homosexuals. The premise is that homosexuality reduces the number of offspring and would lead to the genes carried by a homosexual person to be progressively eliminated over generations. Cochran maintains that the observed level of prevalence of exclusive homosexuality (3 to 4 percent of men and 1 to 2 percent of women in the United States) means genes cannot be the cause of homosexuality. This argument is based on natural selection, the fitness cost of genes 'for' homosexuality being too great for its occurrence at a frequency above that of random mutation (~ 1 in 50,000). The argument assumes that evolution would have largely eliminated homosexuality related to non-infectious environmental causes, except novel ones