She could've instead presented the well documented cases of health risks that arise from primarily male to male sexual encounters and how those end up overlapping and causing widespread infections in communities of color, especially the African American.
if you ignore the fact that 1/2 of all gay people are lesbians who have significantly lower STD rates than heterosexuals, and also ignore that if anything, giving gays the right to marry would more likely
reduce STD rates, and also pretend that elevated rates of HIV infection amongst african-americans would somehow become much worse if we legalized gay marriage, then this is quite the compelling argument you've made.