What's interesting is that today, when I look up the few teachers who seemed to really care, they had significant activities besides teaching, for instance as activists.
As someone who had three activists as teacher during high-school (two literal communist party member and one conservative catholic) I would never, ever want to have an activist teacher in my life, whatever side: they were biased, blinded by their own ideology, hating on each other. What suffered most was lesson quality. They were too occupied to check themselves for ideological purity than for factual knowledge.
The teachers I had were never activists in the classroom ! But this was a different era.