When you had one family drinking milk from one cow, the cow had as much chance of getting TB [and other diseases] from the family as the family did from their cow or each other. But if thousands of people are drinking milk mixed from thousands of cows, and one cow can infect the whole mixture, you have an entirely different situation.
Or maybe you don’t believe in the germ theory.
Healthy bodies are able to resist bacteria, humans and bovines.
The safety record of the raw dairy industry is far better than the the rest of the dairy industry.
Part of this is because they raise their own herds, and rarely add animals from outside. Animals that have been given synthetic hormones are very prone to disease, and early death, and those on the open market are an unjustifiable gamble. Also the source of silage has to be closely watched. Commercial dairies use silage that contains ground up dead animals often. The raw dairies don’t take that chance.