Evolutionary principle of information propagation is universal. Starting from a simple hydrodynamic turbulence and stretching to more complex systems in chemistry, biology, genetics and politics, informational entities procreate as soon as new area suitable for existence is recognized.
In this sense biological organisms are not much different from turbulence vortices. When liquid changes its state from laminar to turbulent, there is a point of instability where an appearance of one vortex cause an avalanche process of recreating vortices first in the neighbor area and finally in the whole volume. One can say that a vortex wants to reproduce. Later they can fight for space killing each other and reproducing whenever possible.
Memes use people as an environment. When mutually exclusive memes clash and fight for survival the most effective solution is to eliminate the enemy meme habitat, i.e. a person who has an incompatible belief. Less severe measures are possible, but they are less effective. As long as people possess mutually exclusive memes, there will always be violence and wars.
Memes as any other evolving things do cooperate to fight common enemies. This cooperation assumes acceptance to some extent to foreign memes. Another acceptance can be to non-hostile or irrelevant memes.