Not speaking out can be a sin, too
The Pope's remarks - that if you swear at my mother, or Islam, "expect a punch" - make me reflect that I abstain from commenting on people's religions on much the same basis that I abstain from commenting on their children.
However, the Commandments (which one assumes his Holiness is in favour of) tell us to eschew false witness. To fail to bear witness at all, when there is harm being done, is also, I would suggest, a sin.
I hope Pope Francis will continue his work in improving the modern Church without expecting anyone's actions, past or present, to go unexamined or uncriticised.