A-Hole's

The world is shocked aliens land on Earth. When attempts to contact the aliens fail, people wonder if an invasion is imminent. The two small aliens who are one inch in height send a rude message they want no contact with inhabitants of Earth. It is made clear they do not like Earthlings. The two aliens harass the world governments by placing obscene statues of their world leaders on the capitol grounds.
They will continue harass the world making it clear they do not like or respect them.  When a large number of aliens land on Earth it is made clear they want to be left alone not wanting to be bothered. The aliens will speak to people of Earth explaining why they find them so disgusting. Inhabitants of Earth are violent, selfish, greedy, and believe they are decedents of primates. They communicate there are thousands of species in the galaxy.
None of them like the Earth and want nothing to do with them.  An invasion from a hostile race of aliens will bring the world together with the aliens as petty differences are put aside. The battle will take a tremendous toll on the Earth. Chances of success is slim. When it ends another threat arrives that will threaten the Earth. It will involve mystical power that the Earth and Aliens are suspicious of.
A sacrifice will need to be made or all will be lost.