Ed Yong’s microbe book, I Contain Multitudes, is stunningly good. Among hundreds of quotable passages, this (p.84) seems of exceptionally general relevance:
We like our black-and-white narratives, with clear heroes and villains. In the last few years, I’ve seen the viewpoint that “all bacteria must be killed” slowly give ground to “bacteria are our friends and want to help us”, even though the latter is just as wrong as the former. We cannot simply assume that a particular microbe is “good” just because it lives inside us. Even scientists forget this. The very term symbiosis has been twisted so that its original neutral meaning — “living together” — has been infused with positive spin, and almost flaky connotations of cooperation and harmony. But evolution doesn’t work that way. It doesn’t necessarily favor cooperation, even if that’s in everyone’s interests. And it saddles even the most harmonious relationships with conflict.