Not because of humans alone, you mean. I don't think that we can remove humans from the game of life. Following that, you could look at it like we're not really screwing with evolution (apart from how you can't really screw with evolution) -- we're changing the environment of whatever we decide to try to save, such that they are no longer considered to be weak. You could think about it in terms of humans in a reverse process: capturing humans and submerging them in non-LCL liquid is basically making them weak, in this context. Kind of a poor example, but I mean to highlight that evolution isn't concerned with strength in an absolute sense; it's about the relationship between life and its environment. Remember that evolution is a process that is not conscious work towards a particular end state.
What I'm saying is evolution isn't racist, and it's all like, relative, man.
Edit: To respond to the topic question, saving endangered lifeforms is cool because we can continue to learn from it, and expand our knowledge. We can't study dead things in quite the same way as we can live things (which isn't to say that dead things aren't worth studying).