Welcome to CC, Jakotis!
Rightly is there concern over false doctrines and those who teach them. Here's a question though: who determines what is "false"? Around here we debate many issues, and it is common for "person A" to think that "person B" (who disagrees with him) holds to false doctrines, and person B thinks the same of person A. Who decides what is true and what is false? Ultimately, Jesus does, of course, but how are we to keep to the straight and narrow in the meantime?