Viruses do not multiply endlessly. Most viruses exist in stable ecological cycles.
Most viruses are beneficial to life. We complain about the few (and tiny minority of viruses) that infect humans and we do so from a selfish perspective, but forget about all the other that make life and evolution possible.
As a matter of fact evolution favors reduced lethality in many cases because wiping out hosts is bad for viral survival.
Agent Smith is way off on this one ...