Gazrok
A True Doomsday Prepper
Personally I would just prefer they don't exist. For the very slim chance such a critter exist, it's best not and try to contact these things and leave it with this phrase 'beware of what you wish for'
Folks have seen too many alien movies.
Here's my take on it. What is the ONLY reason humans go to war? Control of resources. Really. That's it. Now, we may use other crap as a cover story, but in the end, this is the only real reason.
Now, a people that has interstellar travel? Resources are basically infinite. Therefore, they have zero motivation (assuming they have similar motivations we do), for war. Any resource in contest, they simply find it elsewhere without a fight. Hey, there's a planet full of diamonds....here's one full of gold....here's a planet with a frozen ocean, etc., etc.
So, not too worried about the alien invasion scenario. Odds are, their motivations would not be for war.