The problem is free choice.

If we, the human race, decide that aliens aren't real, they aren't. We will never interact with them.

However, it looks like we have decided to enter the galactic stage, and so, expect actual alien contact soon. Within the next decade.

Aliens have already made contact in many, many ways.

And, it is in my estimation, that sending out radio waves is just something to appease the masses.

Govern-cements already know about aliens flying about. Radar stations pick them up all the time. If you get a pair of (correct type) night vision goggles, you can watch them flying about. If you live high in the Andes, you can watch them with your naked eyes every clear night. So, i am pretty sure, that they know that they don't use radio waves to communicate.

What we, as a race need to do is get over our warring tendencies. We have to learn, then make one in ourselves, that war is never the answer.

The idea of an alien race coming to conquer another planet is ludicrous. Just this idea means they we don't know what life is. That we don't know what a planet is.

As an example, people do not lose bone / muscle mass due to lack of gravity in orbit. They are lost because they are not in the earth's magnetic field. So, we do not survive for long on other planets. Conquering is stupid, idiotic, doesn't gain anything, and life is too precious to be going around doing something so stupid.
However, this is not to say that all alien races are nice.