When later authorities disagree with Maimonides or Saadia Geon, I defer to the earlier authorities.
The reason is that I assume that great people like the Baal Shem Tov do not constituent a alternative approach to Torah. And if they would, I would have to defer to Maimonides.
So when I see Hasidic books teaching a different set of teachings than what I know are against Maimonides, I simply ignore them.
I am aware that the Hasidic movement has become highly anti Rambam, even though they deny this fact. The issue is not whether they learn the Guide for the Perplexed (they don't), but rather that most modern day Hasidic teachings are simply teaching Shabati Tzvi's teaching in disguise that neither the Rambam or any of our forefathers would have recognized as being Torah at all. By the teachings of shabati tzvi disguised as authentic Torah the teachings and i think energies of the dark side were able to penetrate into Orthodox Judaism.
This issue of world view is also the reason, learning Musar is important. Too much of modern day Judaism presents a world that contradicts the Torah