Right. I'm not saying eval(their net behavior)>0; I'm saying that if your response function is always negative, you lose the ability to influence their response.
Have you heard the one about the country with the death penalty for all crime? It just leads criminals to maximally try not to get caught, without regard to damage done [i.e. removing all witnesses to even the smallest crimes]. This isn't what you want; even within "negative" relationships both sides lose when you don't have a gradient of responses.