I can sort of relate to how a negative person can create a toxic atmosphere. I play 5 a side with some of the dads from my daughters school. Our GK supposedly played for the Iran u14's back in the day, not sure if this was true but he is really good, definitely a few levels better than us.
He has very high standards, during matches was always shouting, wanted us fat boys to make runs we were simply incapable of making, all in all it was really pissing us off. He's left now (thank feck) and we play so much better as a team as there isnt a cnut shouting at us at every bloody minute of the game.
So, if Ronaldo is creating a toxic, negative atmosphere, get rid of him. This reminds me of Ruud towards the end, it was the right decision by Fergie to move him on and the team performed much better after he left.