A: It is to hate the Munkar and not to accompany its doers; for sitting with them without renouncement is to act like the Children of Israel, whom Allah cursed in His Statement (Glorified be He):
Those among the Children of Israel who disbelieved were cursed by the tongue of Dâwûd (David) and 'Isâ (Jesus), son of Maryam (Mary). That was because they disobeyed (Allâh and the Messengers) and were ever transgressing beyond bounds. They used not to forbid one another from AlMunkar (wrong, evildoing, sins, polytheism, disbelief) which they committed. Vile indeed was what they used to do.