I think they should face censure and never work in education again.
Unfortunately, too many people are unable to see humour, prefering to see racism, etc. instead.
Then social media amplifies it, in a quest to gather "likes", often to boost income.
Why, for instance, bring racial lynching into it? Hanging was a universal punishment, irrespective of race.
US history has too many instances of crowd justice aimed at people of color, thus the noose has become a symbol of white power to people of color. In the US it is seen as a racist hate symbol.