“But, when necessity compels, not those only who are invested with power of rule are bound to safeguard the integrity of faith, but, as St. Thomas maintains: "Each one is under obligation to show forth his faith, either to instruct and encourage others of the faithful, or to repel the attacks of unbelievers" (Summa theologiae, IIa-IIae, qu. iii, art. 2, ad 2m). To recoil before an enemy, or to keep silence when from all sides such clamors are raised against truth, is the part of a man either devoid of character or who entertains doubt as to the truth of what he professes to believe. In both cases such mode of behaving is base and is insulting to God, and both are incompatible with the salvation of mankind. This kind of conduct is profitable only to the enemies of the faith, for nothing emboldens the wicked so greatly as the lack of courage on the part of the good. ” 
~ Pope Leo XIII, Sapientiae Christianae Encyclical On Christians As Citizens.