Sure. I would hope that everyone understands that, especially if the teacher is teaching error in bad faith; i.e., he knows that he's teaching error.
So the worst murderer on the planet, the most foul pervert would suffer no punishment if he was taught that the murders were justified, or that perversion was a higher virtue.
Doesn't follow from your premise. Ignorance that something is wrong is exculpatory, true, but the sins you mention are sins against the natural law. The first teacher of the natural law is God, who writes that law on our heart. Ignorance of the natural law is therefore culpable to some extent. Exactly how culpable in a specific case is of course God's call, not ours.
Catholicism requires a Catholic teacher to teach in bad faith: If he honestly has a difference with Catholic doctrine he is to teach Catholic doctrine.
That is the necessary outcome of a Church that falsely claims authority over men’s minds.
We have seen that ‘natural law’ is easily circumvented by dehumanizing the enemy. Cripples in Germany were dehumanized as ‘life unworthy of life’ and were medically murdered, even in Catholic hospitals.
Keep in mind they did this before the Nazis took over: It was routine to murder crippled WWI veterans. It continued until 1954, long after the Nazis had lost power, but this time they were murdering crippled WWII veterans.