We got the former CNN commentator and current CUNY professor Tuesday on "TMZ Live," where he shared his observations from the demonstrations ... which have led to hundreds of student arrests, but also countless others feeling unsafe.

According to Marc -- who's a former Columbia professor -- most of the protests he's observed have been peaceful, with students simply speaking out against Israel's actions in its war with Hamas.

However, many Jewish students and faculty have been threatened -- some have even been barred from campus for their safety -- and Marc was quick to slam any hateful rhetoric from protestors as "deplorable."

While he staunchly supports the students' right to protest, he points out free speech doesn't mean they can create a campus climate where others feel scared.

He does emphasize this isn't the norm on campus, not in his experience -- but, still, Columbia has moved to virtual learning due to growing safety concerns amid the anti-Israel protests.