[rmlew]

If the Sadducees/Tsadokim were Jews, why wouldn't Karaites be?
Conservative/Masorti, Liberal/Reform, and Reconstructionist Jews don't seem to care much for the Oral Law either, but they are Jews.

[goldstategop]

Because the Written Torah can't be observed without some detailed guidance on how exactly to observe it. This is where the Oral Torah comes in. It does that by spelling out the rules. And Jews agree to be bound by it. Karaites don't accept this so they're not regarded as Jews.

Its true non-Orthodox Jews don't slavishly follow every dot, jot and tittle of the Orah Torah but they don't reject it as the Karaites do. They may sin in not observing it completely but they are still Jews since they recognize that from Mount Sinai, the prophet Moses was given two sets of instructions by God and not just the Two Tablets that became known as the Ten Commandments. To use a kal va homer analogy, if it is true Moses brought down Two Tablets with him, then it is all the more so true he brought down with him Two Torahs to guide the Jewish people for all generations.

(Denny Crane: "Sometimes you can only look for answers from God and failing that... and Fox News".)