Witches are probably just as likely as other humans to have a range of political and ethical opinions. There are people who genuinely think they are doing a good deed by persecuting and killing people working at abortion clinics, people working at refuges for abused women, people of other skin colours, people of other nationalities, people of non-vanilla-heterosexual sexuality, etc.. In some places you will even find one or more of these as the majority opinion. Therefore there are probably witches with those ranges of opinions too.
All the demon needs to do is decide who to give his orders to. It's quite possible that one of the witches will think it's a good thing and go for it, even if the majority may not.
Give half the instructions to one witch, and half the instructions to another witch. Each set of instructions should look reasonable on their own, but together they produce a disastrous result. Combine across multiple witches for maximum obfuscation.
Lie to the witch about what's good or not. (And indeed about whether the demon itself is good or not.) A bit of brainwashing could sway their opinion.
Tell the witch about something true which is detrimental to them or people they care about, as a reason to do something which isn't quite good but will have adverse affects for the person/people they now have a reason to dislike.