From https://hughosb.wordpress.com/2016/11/23/red-wednesday-the-four-cardinals/

'No doubt the Greek considers this an act of fraternal correction. If so, it is far more brutal, far ruder, for more shrill, far less reasoned than the letter seeking clarification from i quattro cardinali. And that is the point: the cardinals are not making a correction, but seeking clarification. But even if they were correcting the pope, why should their act of fraternal correction be condemned yet the Greek feel free to make his own hysterical “correction”. It can only be that he holds an extremely ultramontane understanding of the papal office.'