It is proper, out of love of reason and knowledge, that you do not (summarily) reject anything that opposes your own ideas, especially so if (your adversary) does not intend merely to provoke you, but rather to declare his beliefs. And even if such (beliefs) are opposed to your own faith and religion, do not say to your opponent: "Speak not and close your mouth." If that happens there will take place no purification of religion. On the contrary, you should say at such times, "Speak up as much as you want, say whatever you wish and do not say later that had you been able to speak, you would have replied further." For one who causes his opponent to hold his peace and refrain from speaking demonstrates (thereby) the weakness of his own religious faith....This is therefore the opposite of what some people think, namely, that when you prevent someone from speaking against religion, that strengthens religion. That is not so, because curbing the words of an opponent in religious matters is naught but the curbing and enfeebling of religion (itself)....
When a powerful man seeks out an opponent in order to demonstrate his (own) strength, he very much wants his opponent to exercise as much power as he can, so that if he defeats him his own victory will be more pronounced. What strength is manifested when the opponent is not permitted to fight?....Hence, one should not silence those who speak against religion... for to do so is admission of weakness. (4)
From Rabbi Nathan Cardozo's Thoughts to Ponder