Everyone was gay? Never said that. Lol. Common sense, and the fact babies have been born at all stages of history, disproves that silly strawman.
We’re working on the idea gay people didn’t exist in the past at all. Of course they did. They may not have been called “gay,” prior to that term acquiring its current meaning, but there were other ways of describing same-sex attraction. Certainly pottery and texts from Mesopotamia and Ancient Greece and Ancient Rome, among other cultures, alludes to homosexuality.
Gilgamesh and Enkidu! First epic poem in history! Just one example.