Evolution is certainly aggressive, and rewards aggressive moves. It's all about being able to better use the resources at your disposal as a species to gain an advantage. There's no sense of right or wrong in this selection process - if you proliferate you live on, if you don't you become extinct. There are certainly examples of symbiotic behaviour, but only so long as both parties have an advantage of the relationship. There's no free lunch.

This also goes for infighting among our own species - one tribe continually tries to gain an advantage over others. Just look at global politics to see that this isn't about being fair only about expanding your own territory and power. If you look at what historically happens when a less civilised tribe meets a more civilised (and better armed) tribe it's pretty obvious. The Mayans, aboriginals, eskimos and native American indians have all been exterminated or marginalized in the most vicious ways.