You can never tell if a race is "good" or "bad" until you get to
know them. That is like you going to explore a new culture.
You can't judge them until you have talked to them.
If we never have met an alien then we can't just label them
as good and evil. We must research their species, and then
we can ask those questions.
Aliens are still able to attack, they might be here to watch our
military, or they could be here to vacation.
Who knows? who really cares?
Just go with the flow.