It's pretty clear those in favor of the law view companies's as oppressing and exploiting their workers by making them read email after work to get ahead.
Those against would say it's a question of freedom. Companies are free to make outside of 9-5 email part of the job description, and get rid of people who don't measure up. Workers are free to find jobs where that's not expected.
Not sure the civ-barb axis really fits in that well here, but conservatives might view hard work and long hours as good traits we don't want to discourage, much less outlaw.
https://www.amazon.com/Three-Languages-Politics-Arnold-Kling...