But let's be honest, we all know we would behave like the aliens from Independence Day - mercilessly conquering and harvesting alien worlds and spreading destruction across the universe.

This would be true, except that Star Trek assumes a truly post-scarcity world where nobody needs to harvest alien worlds. Hell, the capitalists (Ferengi) are depicted as ruthless and conniving (oftentimes outright cartoonish) villains most of the time.