Cortez did not decimate the Maya, it was the Aztec. They did not think he was a god, he merely stated it in his letter to the crown that they thus regarded him. There is no evidence that they did. In fact, Moctezuma II did not like him and sought to learn the weaknesses of the Spaniards and crush them. But the Spaniard's committed a massacre in Cortez's absence and now there was a rebellion. Cortez returned and tried to stop it by allying with Moctezuma who was promptly killed by his own people and Cortez and his party were chased out and many of them killed. The only thing that saved him was getting reinforcements from Cuba whereupon he choked off supply lines to the Aztec and eventually destroyed their empire.

So this whole line of reasoning about how so-called aliens regard us is BS.