Mans best friend can also be mans worst enemy, particularly if you are a poor person who doesnt have poultry or other livestock to spare if poultry and rabbit-killing dogs are loose. If you are a villager any dog that wasnt your guard dog would be a threat, and could in fact be important protein and a welcome change from eating more valuable and productive livestock. The practice of eating them probably came about in part as a way to control dogs that prey on farm animals, and continued because they developed a taste for it, and because eating a threat is more economical than killing one of your domestic animals for supper.
One way or another they would have to control the dog population to protect their livelihoods.
That said, it would be better if they were humane about it. There are other ways to tenderize meat.
More often, other men are your worst enemy. For example, progressive sniveling liberals, commies, socialists, and the like are my worst enemies.