[gjulianm]

For one, you're cherry-picking two examples. Some professors don't get fired for jokes nearly instantly and others get immediately fired for abusing their students.

Second, amplification plays a part. A story with "two sides" (such as the joke one) will draw far more public attention than another with only one side, just because there will be more debate and people using it to advance their agendas. In this case, it includes "PC Twitter" but also all of the people who scream "freedom of speech" whenever someone is criticized for saying something dumb or inappropriate.