They are definitely not happy, but they're also slow to take action against Medea.  They cry out, "wretched, evil woman! and "hard and wretched woman," so they clearly reject the argument that she has cause to be angry or take her children back from Jason.  They call the murder of her children (or any murder by a family member) the "polluting moral stain."  However, even when the children cry out to be saved, the chorus stands back wondering "Should I go in the house?" even as the boys are dying.  They wait outside and tell the story of Ino who was driven to killing her own children and who then committed suicide out of grief.