The big question here is drug resistance.
Right now, there is already a DR strain of gonorrhea, found almost exclusively among black men. (The incidence of homosexuality in blacks is also much higher than for other racial groups.) And if the gonorrhea is untreated during its active phase (possibly due to failure of the antibiotics used against a DR strain), it tends to quiet down for decades before re-emerging with serious damage.
And then, of course, is syphilis. If a DR strain of it emerges, it will be bad. It can do horrible things to the body if left untreated.
Especially since there are those who bang pretty much whatever walks, allowing for the disease to reach elsewhere.