That's an interesting perspective and a good point. I would argue though that it would primarily apply at a very late stage. One would have to have exploited all the resources of the home system, then nearby systems, and on and on until hitting the border of the industrial activity of neighboring civilizations. That would require a much longer time than is required for the initial stages of contact.

The Earth is but a small fraction of the available resources in our system. Likewise our system is but a small fraction of resources of nearby stars. To reach the point where we are exploiting the resources contained in the described area is mind boggling. The time scale involved would seem to be orders of magnitude greater than that required to meet and form some sort of relationship with other civilizations.

If we are considering such large timescales then war over resources could and would very well be inevitable. Habitable planets, as a resource, might be worth fighting over relatively soon as well.

Such a war would be short lived. With that kind of technology civs could launch relativistic missiles at each other's planets. They would be nearly impossible to detect since they travel at near the speed of light and could crack a planet in two before anyone knew what happened. Maybe mutually assured destruction would be a deterrent in the event of somewhat similar levels of technology.