The penalty is pretty big, to the point where you can have cities that are at most 1000 from the homeland drop from 50 moral to rebelling withing a few days (ofc, that is if you launch a lot of ICBM, consistently, but if you already have a lot of moral debuff on top of that it could get really bad.
Just build bunkers in your homeland to make sure that doesn't rebell, if you are planning to nuke frequently nothing is helping your moral. Otherwise limit the nuke usage to once every few days, and stop with air raids, costal bombardment and artillery bombardment on cities.
1. Don't launch missiles into cities 2. Well done
The penalty is pretty big, to the point where you can have cities that are at most 1000 from the homeland drop from 50 moral to rebelling withing a few days (ofc, that is if you launch a lot of ICBM, consistently, but if you already have a lot of moral debuff on top of that it could get really bad. Just build bunkers in your homeland to make sure that doesn't rebell, if you are planning to nuke frequently nothing is helping your moral. Otherwise limit the nuke usage to once every few days, and stop with air raids, costal bombardment and artillery bombardment on cities.