Chimps are bad news
I believe the problem is that adult chimps are just as obnoxious, bad-tempered, violent and downright murderous as their cousins Homo Sapiens. Just 6x stronger! Thus they are very hard to control, and capable of dishing out extraordinary amounts of damage to the comparatively puny human physiology.
Those few crazed humans that think that the best way to to save the planet is to destroy mankind in its entirety really should consider taking out the chimps, too. Leave the world to the gorillas (deceptively gentle giants) or to the bonobos (too busy having to sex to be violent).