There have to be consequences for actions like that. If there are no consequences, then yes teaching will become impossible.
The thing about classroom control is that it is easier to notice early signs and stop the situation from escalating into behaviors that need to go through a whole punishment process (possible student trauma, paperwork for the teacher and administration), and so teaching how to correct things early and keep things controlled is a win-win for the student, teacher, and administration, and also the rest of the class.