Scandal causes havoc even among those committed to the Lord.
St. Alphonsus: "a single bad book will be sufficient to cause the destruction of a monastery."

Pope Pius XII wrote at the beatification of Blessed Maria Goretti (1947): "There rises to our lips the cry of the Saviour: 'Woe to the world because of scandals!' (Matthew 18:7). Woe to those who consciously and deliberately spread corruption in novels, newspapers, magazines, theaters, films, in a world of immodesty!"  Yet today multitudes of Christians fail to guard themselves from this evil.

Let us experience the sorrow of the Lord due to scandal. That is the best protection against them. Then we will not cause scandal nor crumble on account of them. 

Scandal of Churches making business with sacraments -Pope Francis, 2014.