I disagree that this has to be a zero sum game. There are many courses of action that could have been taken before, during and after the lecture by the lecturer

I disagree that this has to be a zero sum game. There are many courses of action that could have been taken before, during and after the lecture by the lecturer, the students who felt affected by the lecture, and the faculty administration, none of which would have to involve punishing anybody and that would have led to a better outcome. For example, somebody, somewhere, could have created a forum for a more socratic method to discuss these images and people's reactions to them to help improve understanding on all sides. Saying "I'm going to do something offensive, and if you're offended that's your problem because I've told you, and I've told you I don't care about that offence", is about as constructive as a response of "I have been offended, and even though I was warned I was about to be offended and did not take the appropriate measures I was offered to protect myself from that offence, I will complain that I was offended". Rhetoric (in the philosophical teaching sense), is a hell of a move to double down on when you're dealing with topics where the discussion itself can have real consequences. It is not a "tired liberal relativist platitude" to suggest that a contributory cause of the issue here was all sides involved stopped caring about consequences to others, and instead all erred towards self preservation while maintaining an insistence that rhetoric will work and dialectism would fail. Self-preservation might be rational as a mammalian instinct, but in a philosophical setting (and a lecture touching on images of theological subjects surely is such a context), it's that conservatism that is tired and relativist: true liberalism (not libertarianism), was the essential lightning rod that was missing from the conversation.