Is it permissible for a student of knowledge to refute a shaykh who mixes Islamic knowledge with falsehood, in order to save students from being influenced by him, and how should the refutation be?

It is feared that the fault lies with those who rush to discredit and malign without verification. The اصل (fundamental principle) is to revere the people of knowledge, recognize their esteemed status, and seek excuses for them. No one is infallible, and everyone's words can be accepted or rejected. It is not permissible to slander merely based on whim. If one is certain of a scholar's error, then explaining their error with knowledge and justice, by someone capable of doing so, is commendable, provided it adheres to the bounds of not exceeding limits, preserving the scholar's standing, and seeking excuses for them. The intention should be sincere advice and clarification of the truth, not mere disparagement.