Cancer is very dumb, by any metric I can possibly imagine:

• it literally lacks any mechanism for intellect/processing information
• it is a random mutation that renders affected cells dysfunctional
• it has no mechanism to spread to another host, yet still kills the host it has
• it has four different ways that it might just kill itself

This only makes the metaphor all the more apt. Intelligent foes are far less dangerous. You have to be exceedingly dumb to choose mutually assured destruction.