How do I deal with a fool?
When confronted by a foolish person, Mishlei warns us, “Al ta’an k’sil ke’ivalto, pen tishveh lo gam atah” (Do not answer a fool according to his folly, lest even you become like him). The very next pasuk (verse) seemingly advises the opposite, “A’nei k’sil ke’ivalto, pen yihiyeh chacham b’einov” (Answer a fool according to his folly, lest he see himself as a wise person in his [own] eyes).
The Gemara resolves this contradiction by explaining that the two verses refer to different subject matters. If caught in conversation with fools on worldly matters, al ta’an—remain silent and do not stoop to their level. On the other hand, in Torah matters, we have the responsibility to correct their misconceptions and not allow our silence to be interpreted as assent, so that they do not perpetuate their fallacy and think themselves wise.
There are other situations where we need to weigh the wisdom of speaking up versus remaining silent. If it’s possible, we should take the high road, answering with mussar (gentle reproach) and clear logic against flawed reasoning—without engaging in the fool’s own coarse lingo or narishkeit (nonsense). There is also greater merit to engaging in a discussion when among strangers, where silence may otherwise be construed as consent to the foolish talk—versus in one’s own community, where it would be inappropriate to converse with a known fool.
When challenged by someone who will obviously not be swayed, we should not become involved in lengthy discussion. Especially when dealing with an apikores (a heretic, i.e. a Jew knowledgeable in Torah who nevertheless rejects the truth), we are obligated to turn a deaf ear to their narrative.