The implicit message is that the "us" cannot trust the "they", and writers like Paul Graham show the reason why: Any attempt at social change can easily be labeled a virus by capitalists if it does not produce greater prosperity. It's the same prosperity that has poisoned the earth, so I hope they have answers there too.
Yes, this origin is correct as I remember it. I first heard the term publicly from Larry on his show a decade or so ago, mainly referring to police interactions. He presented it well using comedy, unlike the rabid versions of today. He presented it too well as today, it seems this movement has since taken over by (mostly) white college people to service their own selfish ends; that's the mind virus part.
This clip pretty much encapsulates this idea: