I circle around UCLA’s Moore Hall for the third time. Security officers block each entrance. Police in riot gear patrol the streets. Metal fences wall off the building from protesters, and barricades separate protesters on the left from those on the right. Everyone prepares for Donald Trump Jr.’s arrival to promote his new book, “Triggered: How the Left Thrives on Hate and Wants to Silence Us.” As a trauma therapist who works with women and refugees — and who practices on Canada’s west coast — I admit that I live in a progressive bubble. I’ve never met a Trump supporter...