Actually, this is a great misconception; some of the toughest and dreaded fighting forces have, in fact, been gay. For instance, the Spartan army and the Waffen SS.
The real problem is that gays have a corrosive effect on societies that inevitably, judging from history, causes them to disintegrate. Other than that, there's no reason to oppose their agenda.
Their agenda is destructive, to children and society. It is hedonistic and self-centered. Their self-descriptor revolves around what they do sexually. It is their primary focus.
I’m not much into history - cannot even imagine what a “tough” gay army would look like. Nice outfits, and skilled marksmen? “Kill them!! Do my eyebrows look ok?”