That's not true at all. There are pretty specific words that could be triggering to someone, professors usually know what they are and typically they either avoid the words entirely or give students plenty of advanced warning through the syllabus and pre-class discussion about the reason (ex. wakelaw13) why the word is going to be announced aloud. I'd bet (obviously wasn't there) that some of those steps weren't taken in this case, based on my experience in and teaching the classroom.
The "any word can be triggering" is so hyperbolic, c'mon. And I'm not saying discussions of rape, abortion, poverty, racism, and any other difficult topics shouldn't be broached carefully. I'm saying that the words that pretty clearly are pregnant with hate and derision don't need to be distigmatized, and any academic presentation that just assumes students are familiar with the historical and emotional weight behind that word (introduced without this backing) runs the risk of drawing fire from wounded students.