I sometimes undermine DH when it comes to discipline. I know the problems with this. I need to work on it. Partly it's because i sometimes think he has been too stern. Usually it's minor but this seemed more significant.
If your child was playing up - big time - and your DH had lost his cool, was telling him to go somewhere we all needed to go and in the end shoved him that way, how would you react?
I said not to push him, and took over the situation. I thought the occasion warranted it.
I know what its like to lose your cool with young children, we all do it. But I would be grateful for somene else to step in and would reflect on how I had managed the situation badly. DH felt undermined.