aliens will not be friendly

[Cruzincat]

The OP misses some logic in his theory.
1. If aliens have discovered the Earth already they have discovered we are either too violent and backwards for them to care about getting to know us or we have absolutely nothing they want.
2. If they haven't yet discovered Earth and when they do they immediately contact us then you would have to fear that they are more advanced and do not fear us, and/or we have something they want.

If 1 is true and they do finally make contact, then you have to worry about what they might want from us, because up to that point they didn't care enough to make their presence known. The fact that they are advanced enough for travel of that magnitude does not automatically make them better than us in all or any way you can think of, however, I would not want to be in the open for quite some time when(if) it happens.
If 2 is true we are ****ed!