The Council could discourage being trained in sith alchemy or to dark side magic but it should be okay to learn about things that they should able to defend against. This was one of my main issues with the Jedi in this era. They can not defend against a scream. Jedi Council Masters should theoretically have knowledge of these things. Yoda and Mace appeared to be the only ones capable of understanding how to defend against Palpatine. Mace as we know uses Vaapaad and then there is Yoda who appears to have a vast amount of knowledge on many things including the dark side.