Aside from the fact that it is a silly picture, any button to release the "chemicals" would not be labelled what that chemical would do, it would simply be labelled "chemical release" or something. Not for any nefarious reasons, but for the obvious fact that you might not want to use the same chemical every time. Sometimes you spray for population control, sometimes for mind control, etc.
IOW, the button in a bomber is usually labelled something like "bomb release" (if it is labelled at all), it isn't labelled "people killler".
(i can't believe i just wrote all that)