Why do we respond to the Wicked son in such a harsh way that we "strike him in his teeth?" Isn't it at least to his credit that he is here, sitting around the seder with his family?  Isn't that good enough?

Rabbi Shlomo Carlebach of blessed memory explains a teaching from the famous Belzer Rebbe, Reb Aharon Roke’ach zt"l. 'Reb Ahrele' taught that everything in this world, every aspect of reality, has within it a pnimius and a chitzonius, an inner and outer essence. The word for the wicked son, (Rasha) is spelled in hebrew ר-שׁ-ע. The outer letters are ר-ע which spell רע - evil. That is what this person is - but only on the OUTSIDE! The שׁ, which is the letter on the inside, has three branches, each representing one of the 3 forefathers of the Jewish People, Abraham, Isaac and Jacob.  And that is the "pnimius," the INNER manifestation of this holy so-called "wicked" Jew.  Despite his evil wayward lifestyle and attitude, in the merit of the Avos/forefathers, he is also included in this redemptive relationship with God.  Even the wicked son is filled with heritage and positivity.  

Reb Shlomo says, do what the Haggadah says to do to the Rasha, strike his teeth/Shin[av] – his שׁ – his inner manifestation – agitate, stimulate and arouse the Shin, namely, the awareness of our forfathers to awaken the body to the existence of the Soul.

haggadah Section: -- Four Children
Source: Rabbi Shlomo Carlebach zt'l