Wow, this is like high schoolers arguing about quantum physics. Understand the problem before you start complaining about the solution.
Let me put it this way. Instead of "you are responsible for the collision," a better phrasing would be, "had what occurred on your front end happened in reality, you would have collided." Does that make sense? Moreover, had what occurred on the other guy's front end happened in reality, he would not have collided.
"Seeing" and "responsibility" really have nothing to do with it. It's not an attempt at dealing justice of some sort, it's simply simulating what would happen under the circumstances each pilot sees as accurately as possible. It is physically impossible, at least with today's technology, to perfectly simulate a two-player collision over the Internet. Having it so that what happened on each front end happens on that front end is the best compromise by far. The only viable alternative is no collisions, which is a lot more unrealistic.
The argument I seem to be hearing is, "If it comes from underneath, there's nothing I can do to avoid it. Therefore I shouldn't be 'punished' by a collision when the other guy isn't." Well, if it came from underneath in a real aircraft, there's nothing you can do to avoid it, but you're still going to collide. The only difference in the simulator is that the other guy goes unscathed because, on his front end, he did not collide.
In summary, in a perfect world the result of an online collision would be both planes being damaged. This is impossible. The next best thing is having only the aircraft which would have been damaged in reality, given the circumstances occuring on his front end, actually be damaged in the simulator.
