If aliens or some other kind of sentient beings are discovered, then they are actually annother race. Yes, different ethnicities of humans have minor biological differences, but we're all just part of the human race. Besides, there are people out there that discriminate and hate people just for skin color. Imagine how much of a scapegoat people if annother species entirely would be to the ignorant!
Based on modern relationship between different races and different countries, a future relationship with intelligent alien life isn't going to be smooth and simple.
If we have to compete with this alien civilization for resources and territory, I'm afraid our relationship with it will be difficult and potentially perpetually hostile. The best way to deal with intelligent alien life will be to remain distant and reduce our contact.
We humans have enough trouble on planet Earth as it is.
If we discover some kind of being in the universe that is its own civilization, inevitably there will be people that hate it because it's different and are immediately hostile towards it. People like that will always exist on that planet, if some of us can't handle different looking types of humans we're certainly not going to be receptive to a different species.
As man reaches to the stars, we will eventually find new intelligent creatures. As with the introduction of anything new into human culture, it will be both revered and reviled at the same time. Humans will complain initially about special privileges and the consumption of Earth born resources. Humanity fears what it doesn't understand.