Yeah, there weren't genocides to the extent of those in WW2. I suspect that WW1 would have occured without the assassination: Austria deliberately sent a list of demands to Chezchoslovakia that it knew would be rejected, and when it was, Austria invaded. So it was just an excuse.

I think Rich was referring to the chaotic nature of diplomacy: Ferdinand's death triggered WW1, which lead into WW2 (Versailles left Germany really REALLY pissed off.) So the small acts we take now may result in much death later.