It might be doable if you scratched the order=deatheaters idea. You could make them look like deatheaters, or stage attacks. Or Dumbledore could manipulate them into thinking there doing good but in reality its bad. Or he could be obliviating them. It doesnt matter, in any case the order+dumbles could be bad without being the deatheaters.

It could really all just be a manipulation of press coverage. Dumbledore kills family A. Family A friends (deatheaters) strike back. No one knows what dumbledore did, but suddenly deatheaters are criminals/villains.

Voldemort could spout his crap about the magic/technology and how its a good step.... But who do you believe the man whos name everyone is afraid to speak or the perceived leader of light...