But sorry you lost that fight when they started using the word to mean someone who does something for a living. If you can say someone is a professional painter how does it make logical sense to turn around and say they are not a professional? To make things worse once they started using the term unprofessional to describe someone who was not conducting themselves in an acceptable manner it really can't be shocking that people start objecting to being told they are not professionals.

Basically once they started using the word started to mean something beyond the narrow definition of of a few select careers that “professed” to a code of conduct this creep was inevitable.
We can argue what we think a word should mean but when the dictionary meaning doesn't match usage it really just come down to opinion. In the end words mean what people think they mean