Parent A
Parent B
DS (7)
DS 7 had a friend come round to play after school. Unbeknownst to Parent A and B, friend had gone into the parents' bedroom and jumped up and down on the parents' bed. DS didn't stop the friend, although insists he didn't join in.
When friend went home, Parent A was annoyed that DS didn't stop friend from entering his parents' bedroom and jumping on the bed. Parent A told DS that they couldn't watch the football on the TV that evening. DS was upset and cried for 5 mins. Then was fine.
The above is just some background context for the following:
Half an hour later: Parent A and Parent B are upstairs with DS and getting him ready for bed. Everybody's mood is fine.
Just before getting into bed, Parent A plays a game with DS. Parent A won't play the game the way DS wants them to. DS gets upset. Parent A refuses to back down.
Parent B intervenes to calm DS down. DS calms down and says he wants to watch football. Parent A says that no he can't due to earlier events with friend. DS gets upset and starts crying. Parent B tries to calm DS and regulate his emotions before bedtime. DS is still upset and whining. Parent A says "I'm going to kick off in 30 seconds if you don't stop. Do you want me to kick off?"
Parent B is aware that Parent A's kicking off means shouting loudly and getting angry. Parent B says "ok guys let's tone it down".
Parent A is now angry with Parent B for undermining them and left the bedroom annoyed.
Is Parent A justified to be angry with Parent B?