Homeopathy is woo-woo at its worst. But it seems plausible that the majority of practitioners believe as much in its efficacy as do patients. When you say they are selling lies, you ascribe malice where self-deceit may be the more likely explanation. Of course, no manner of good intentions will help those desperately ill people who would have been better served by conventional medicine.
Oh yes, I believe ignorance and self-delusion is more common then malice. However that doesn't excuse them totally. When it's literally a matter of life and death for someone else, you have a moral duty to ensure you're giving the right advice.
But they are not careless from their own point of view. I daresay they are more intensely passionate in seeking out the latest knowledge in their own field than your average family physician. Breaking out of an inculcated intellectual and epistemological framework is an almost impossible feat.
I would make an analogy to veganism. Vegans as a whole are more intensely interested and passionate about their health and what they eat than your average healthy omnivore. For that reason, they're also more likely to proselytize and promote their ways to others. It's my belief that in doing so they potentially bring harm to themselves and to others. Do I think they should be engaged in vigorous debate and their arguments refuted to the best of scientific knowledge? Yes, absolutely. But I don't think treating them as idiots or malefactors is well-deserved or productive.