It’s not just union jobs that are affected by the increase. I have a neighbor who has mostly conservative ideas but still thinks these increases are a good idea. He’s in management where he works. Years ago we were discussing the $15 min wage and he was for it. He claimed that it wouldn’t affect his company as his company’s stating pay was about $16 per hour ( over twice minimum wage ) at the time. He said “my company doesn’t start people at minimum wage.” But he still couldn’t make the connection that an increase to $15 would automatically put their starting employees just next to min wage. That’s the mindset we’re dealing with.
Also, unions and workers do coercive comparisons on wage differentials and will try to maintain that spread. If your friend’s employees used to say “I’m earning twice the minimum wage.”, they will continue to try and maintain that wage spread, hence an upward pressure on non-minimum wages, too.