I am doing a research paper on Wicca and I'm really having trouble choosing a strong thesis. I was thinking arguing how Wicca is not evil. How is that?
By creating the thesis "Wicca is not evil," you immediately prejudice the reader. In a sense, you, as the writer, are assuming that the person reading your paper believes that Wicca may be evil.
Ask yourself the following questions: What do I wish my role to be as the writer? Would I like the reader to view me as an objective, realiable source? Would I prefer that the reader view me as subjective and, perhaps, unreliable?
RAFT is a good start. What is my role? Who is my audience? What is my format? (In your case, a research paper.) What is my topic? (In your case, Wicca.)
With that said, your thesis is also too broad. Because it is too broad, you may find yourself having issues with keeping your ideas organized. Consider narrowing your thesis to something more specific. If I were to manipulate your thesis (in a non-threatening way), I might write something such as: "Misconceptions cloud spiritual practice Wicca; this paper will shed light on the most common ones and examine their merit." Now, you have more focus as a writer. You know exactly what you are going to discuss.
Again, when you are making thesis statements, your goal is to keep them narrow, focused, and manageable.