Why will the Maskil be quiet?
Rashi: He is a Chacham. He is quiet when evil comes, and does not question Midas ha'Din, for they did all these [evils].
Radak: Because [the Resha'im] hate one who rebukes them, the wise Tzadikim are quiet and do not rebuke them, lest he hear the reviling that they reply.
Malbim: The Maskil knows your evil way. Normally, he rebukes. Now he is quiet, for it is "Es Ra'ah" (refer to 5:13:2:3).
What is "Es Ra'ah"?
Rashi: It is the time for them to receive their evil.
Radak: It is when the evil have the upper hand.
Malbim: Resha'im hate one who rebukes and kill him - San'u va'Sha'ar Mochi'ach" (10). Therefore, there is no hope that they will repent, and no one raises them.