Nerds Are Taking Your Lunch Money
dilbert.com
dilbert.com
Obviously anything to do with Nazis or the Holocaust triggers this reaction faster and more severely, but it can happen with any subject. Every argument of "Currently A is happening. When A happened in {time/place} it led to B and then C, and we all agree B and C are really bad" will be met with "How dare you compare yourself to {time/place}! B and C aren't happening now and will never happen again" (with no explanation for what will prevent B and C from happening).
You and I may be moderates, but you have to agree, there definitely are more than enough people who would support mob justice (to take a mild example, the attacks on Google's buses recently... the entire situation seems like a powder keg)