It is mentioned in Yerushalmi (Sanhedrin, 87, Halacha 13) that a magician/ witch (Mechashef) applied his magic on three Taanaim: Rabbi Yehoshua, Rabbi Lazer and Rabbi Akiva in a public bath house. How can it be that the magic really work on these great Taanaim, whereas it did not work for Rabbi Chanina Ben Dosa (Yerushalmi, Hagiga, 82, Halacha 2) since he did not believe in the witch. Moreover, it is known that whoever believes that there is nothing but G-d (אין עוד מלבדו), the magic will not work on him?
The Gmara asks some question like that in Sanhedrin 67b:
ההיא איתתא דהות קא מהדרא למשקל עפרא מתותי כרעיה דרבי חנינא אמר לה אי מסתייעת זילי עבידי אין עוד מלבדו כתיב איני והאמר רבי יוחנן למה נקרא שמן מכשפים שמכחישין פמליא של מעלה
There was a certain woman who was attempting to take dust from under the feet of Rabbi Ḥanina in order to perform sorcery on him and harm him. Rabbi Ḥanina said to her: If you succeed, go and do it. I am not concerned about it, as it is written: “There is none else besides Him.” The Gemara asks: Is that so? But doesn’t Rabbi Yoḥanan say: Why are sorcerers called mekhashefim? Because it is an acronym for: Contradicts the heavenly entourage. This indicates that one should be wary of sorcery.
So the question is : does sorcery really exists ?
The Gmara answer:
שאני רבי חנינא דנפיש זכותיה
Rabbi Ḥanina is different, as his merit is great, and sorcery certainly has no effect on such a righteous person.
So this is a "special" point of Rabbi Ḥanina, not because he said אין עוד מלבדו, but as a special person (as there are a lot of "special" stories about him not dying by snake, about vinegar burning for him etc.).
I personally would have say that the Gmara say that because she herself believes in sorcery, but I do think it is possible that Rabbi Ḥanina would not have believe at all in sorcery, and would not agree with Rabbi Yohanan's drasha.