Nisan-Fighting the Fire of Anger XVII-Tzemach Tzedek

The 13th of Nisan is the Yahrtzeit of Rav Menachem Mendel Schneerson, the Tzemach Tzedek, third Lubavitcher Rebbe: The Tzemach Tzedek was accustomed to restrain an angry rebuke until he had reviewed the Halachah whether anger is permissible in the particular instance. But how much genuine anger could he feel after searching for the authority of the Shulchan Aruch (whose Yahrtzeit is on the same day; Nisan 13)? (Ohel Naftali, page 56)