The "Open Book" author was leaving Il Mulino restaurant in NYC after midnight when she was accosted by some anti-fur protesters who shouted out "animal abuser," "murderer" and "shame on you" as she hopped in her SUV.

One guy hammered his point home by screaming ... "What type of person would wear fur in 2020?!"

This wasn't Jessica's first run-in of the day with the angry activists. Earlier Tuesday night, her Barnes & Noble book signing event for her new memoir was crashed by a much larger group of anti-fur folks.

They began screaming and holding up their signs as Simpson came out to give a speech, forcing her to take cover for a couple minutes while security booted the protesters.

The good news for Jessica ... her fans stuck around, chanting her name, and she eventually came back out and talked about her book.

BTW ... if any of the animal rights activists look familiar, it's because this isn't their first rodeo. They've crashed events and confronted several other celebs for wearing fur ... like Kate Upton, Chrissy Teigen, Lil' Kim and Jennifer Lopez.

We're certain they'll do it again too.