It’s unclear how it would work. No one knows what it would cost. And it’s anyone’s guess whether it will ever actually happen. But in the days since Donald Trump floated the seemingly crazy idea of slapping tariffs on foreign-made film and TV productions, something unexpected has started to happen in Hollywood: befuddlement has turned into murmurs of approval — at least in certain corners of the industry.

“This is the first time I’ve ever seen this kind of divide,” says Diego Mariscal, an IATSE member who runs Crew Stories, a popular online forum for below-the-line workers. “People I’m talking with are saying, ‘At least Trump’s doing something. When’s the last time a president even tried?’ He’s creating a conversation.”

That conversation, like so many sparked by Trump, is sorting itself along sharply drawn class lines. While the executive class is almost universally...