Ins Gesicht sagen — to say to the face. Offen aussprechen — to speak out openly. Kein Blatt vor den Mund nehmen — to take no leaf before the mouth, meaning to speak without covering.
And the opposite: hintenherum, behind-around, and hinter dem Rücken, behind the back. Both are accusations.
The German objection is not to being criticised in front of others. It is to being criticised where you cannot answer.