Mdd, in the interests of intellectual honesty, I will bring you a rayah, but it may not be conclusive.
The gemara says if a man was mekadesh a woman al mnas sheani rasha, afilu tzadik gomur kol yamav mekudeshes, shema hirher dvar avodas kochavim blibo. It is mashma that the thought alone can make someone a rasha. But to defend my point, in that case it was a thought to actually do avodah zara, and I believe that such a thought, even if he does not carry it out, HKBH metzarfo lemayseh.
I need to think about it. I also want to look up the gemara about Elisha ben Avuya who saw someone doing kibud av and shiluach hakan, and the person died. Because of this Elisha ben Avuyah became an apikorus. Why did this make Elisha not believe in schar mitzvos? Maybe the person was thinking an apikoreseshe thought at the time and deserved to be punished. Yet the gemara, I believe, does not explain the reason for this person’s death that way. It instead says he died because schar mitzvah bhai alma leika.
I need to look up and think about it, but tired now.