DOC DOOM! (not to be confused with MF Doom)
For starters, here is what he is actually saying.
There's nothing too radical or shocking about it. It's a scientific warning about the vulnerability of the worlds human population to pathogenic microbes, which is something we should all know about and be grateful to be made aware of. His 'infamous' speech made waves simply because he 'took the microbes side' to make a rhetorical point. The point: We are now in serious, serious trouble because of our overpopulation and treatment of the worlds resources, and the microbes have us at a serious disadvantage because of it. Is there anyone actually dumb enough to think that this speech was a serious call for destruction of 90% of the world's population by human means? Apparently so.
Edward Abbey, in one of his funnier moments, once told a hall full of cattle ranchers that their cattle should be hunted to extinction and their bodies ground up into coyote food. He too was making a rhetorical point; that cattle require more land in the southwest than they are worth, and that they destroy the habitats of indigenous animals like the coyote. This point, whether right or wrong, was at least understood by the audience. The ranchers didn't immediately rush out and form cattle protection militias, or start waving signs that said "Save our Cows!" or even report Abbey to the 'Cattle Police.' They realized he was stretching words to make a point, told him what to do with that point, and went outside and shot their pistols in the air.
Unfortunately, this kind of lively, imaginative debate is proving a tad too subtle for today's right wing reactionaries to handle, which is why Mr. Pianka has been singled out for surveillance by giddy little informants like dickhead here.