They are not worshipped. They are basically the upper class. If a Sith is disgraced, which does happen, his or her entire family is enslaved.
The reality is that the developers themselves were not going to include sith pure bloods as an (initially) playable option within the Sith Inquisitor class because it did not easily fit within the story line. They raised the concerns, not me. It is in one of the development videos.
I'm personally glad they did so people like you could come up with an interesting back story to make it work.