The Big 3 asked for this. Tesla can at least defend themselves, justifiably, by saying "we lowered prices at every chance we could" and "our management's compensation, like the employees, is tied to both company and stock performance". The Big 3 lined their pockets, and now want their employees to not share in those benefits.
I'm staunch anti-union, but I can't fault them for wanting something that trends in line with what management gets. My main concern is that there will be blow-back on wage pressure at Tesla.