While it is true that dairy is a no no for people with candida, butter is different and causes no problems. The reason is because the higher the butterfat content the lower the lactose (sugar).
When I had candida I was extremely sensitive to all dairy products, except butter. At the time I was so ill that I could only eat 9 foods in the whole world (I had no choice because everything else came back up) and butter was one of them.