"Maybe it says something about human nature, that the only form of life we have created so far is purely destructive."
Other (constructive) computer programs could just as well be seen as a form of life. The difference would simply be that one spreads without our immediate consent and the other needs to convince us that it is useful to us before being allowed to spread (kind of like pilot fish). Both use a combination of pre-existing infrastructure/ecosystem to procreate - our brains, computers, language and other methods of communication.
They are all the form of life called memes or temes by Susan Blackmore (http://www.ted.com/talks/susan_blackmore_on_memes_and_temes....). (Also Dawkins et al)