My STBXH often told me to shut up. He didn't and still doesn't think there is anything wrong with it.
When my 10yr old son told me to Shut Up (I chastised him for saying it but he didn't see a problem - 'Why not say it to you, Dad does?) I was beyond upset.
I know that my EX tells our children to Shut Up. Last night my DD phoned wanting to come home because her Dad had shouted at her and told her to Shut Up again. Am I over reacting to be so upset that this is how he speaks to our DC?