They also dont want a lawsuit because a sick employee couldnt afford healthcare and had no sick days left, so he went to work and infected a dozen vulnerable patients with a disease that turned deadly for them.
Employers have a lot of options. They can threaten to fire people in large numbers, they can threaten various things, but by specifically threatening to cut off health care, their trying to put the workers to a life or death decision. In other words, this particular approach is definitely immoral and unjustifiable.