I'm not well-informed with concern to homeopathy, but generally, have considered it a largely harmless pseudo-science akin to the faith-based, crystal, pyramid-hat, etc., healing "arts". I have no qualm from its practice as it is relegated to the nebulous confines of Naturopathy whose proponents and patrons know it is an alternative medicine, therefor, carrying an implicit "buyer beware" sign written in bold type.
The question of "ethics", as in most regards where a product or service is for sale, is of variable determination and usefulness. I doubt there is little difference (or remedy) to be made with regard to automotive repair mechanics.