Note too that the word "parasite" is invidious. To them, WE are just the environment in which they live- their country, their planet. That they have as little care for or interest in the wellbeing of that planet as most humans do of theirs is not their fault- they don't claim to be intelligent. Some of them totally destroy their own world by using up its resources without constraint, and in some cases the world reacts by destroying them- but they have the option of dispersing their offspring to other nearby planets. We aren't even remotely near being able to do this yet, so when our host dies or kicks us out, that's it.