Would Aliens Really Kill Us, 'Independence Day'-Style?

In the new movie "Independence Day: Resurgence," opening in theaters today (June 24), Earth will once again gear up for an epic fight with a hostile alien race. The premise will set up some awesome action sequences, but how realistic is the idea that if aliens were to visit Earth, their one goal would be to destroy us? Twenty years ago, the new movie's predecessor, "Independence Day," featured Will Smith and Jeff Goldblum cracking wise while using a computer virus (presumably written in an Earth