Everyone should remember that there is a difference between lactose-intolerant and dairy allergy. Lactose is a sugar. An intolerance can be easily assisted with an enzyme. That is not the case with an allergy which is based on the protein.
Just because yogurt has good qualities doesn't mean it is good for everyone. Casein and lactoglobulin are the main proteins in milk, and if they remain in the product in any amount, it can cause a reaction in an allergic person. There are other ways to get probiotics, and to encourage probiotic growth within the digestive tract. I would suggest that any allergic person avoid all dairy products and do a little research for alternatives.
And yes, I have had homemade yogurt, and it tastes wonderful. I still reacted. Same with kefir and whey. If you are allergic you are allergic. Even in yogurt, the casein and lactoglobulin remain.