Not terribly original, but the real problem is that I'm having a hard time believing that world with real magic could produce a civilization that's scared to death of it.
I'll cite the words of Arthur C. Clarke, two possibilities exist: either it's magic or sufficiently advanced technology, and something about morality hijacked by religion.
Think a minute about your smartphone. If you don't have one, think about somebody else's smartphone. We may not know
how it really works, but we understand this is a Chinese-made machine that does a set of task it is designed to do. There is a number of people that are thoroughly addicted to it though, it emits and receives EM waves which can cause cancer, it can be used to spy on you even if you turn it off.
Some people are scared of it. Maybe not scared like panic attack inducing scared, but enough that they think it is so detrimental to their lives that it will drive them off smartphones, or technology in general. There is a very real movement of people living off the grid, whether it's to be closer to nature, to flee the woes of modern life, because of electromagnetic hypersensitivity, or some other reason.
"Where is he going with that?" says the reader.
My point isn't to say these people are lunatics, because we're possibly the lunatic ones blinded by technology, but to say these people made a choice. Despite all the benefits of science, research, despite thousands of years of civilisation driven by some technology or another, these people made the choice to cast their technology off and go backwards. That thing you think is so great and you take for granted, they reject it out of principle.
Magic and technology aren't that different. Why wouldn't a medieval peasant be willing to cast off magic if they felt magic was bad?
And it's so very easy to justify too, and that's also where morality and religion come into play.
You hear something enough times and it becomes truth. It's that much faster when said by someone you regard as authority. With a powerful Church and an entranched fear of God, you can convinced villagers rather easily. They might be skeptical at first, but just wait and hear the stories of evil mages propagate.
They'll believe it. They'll believe all of it. They'll believe magic is wrong. They'll believe even more if it's the will of God. Eventually the hatred of magic will be so entranched you'll just have to point your finger and say "this one made kids stay up past bedtime" and they'll burn a witch down.
I'll add that it doesn't have to be global and universal. In fact, that justifies burning witches in some place just as easily as it justifies people loving magic in other places, which might be something interesting to explore.