Why do we look at death as a bad thing?

[Psychonaut]

Well, evolutionarily speaking, species that fear death are favored.

I second this, there's also a growing body of data that suggests that a lot of mental pathology is caused by trying to rid ourselves of this instinctual death anxiety in maladaptive ways.

The theory also posits that humans tend to resort to violent behaviour as a means of defending their death transcending mental constructs (IE:- culture, religion) and gives a decent description of why we fear death. Check out terror management theory if you're interested (there's also a great documentary with Sheldon Solomon called flight from death).