In the sicha of Yud Tes Kislev 5693 (which is printed in Likutei Diburim) the Frierdikker Rebbe writes that the Alter Rebbe was released after Mincha but was mistakenly delivered to the home of a Misnaged where he was caused much more distress than his imprisonment. He adds that the Alter Rebbe was not concerned at all with his physical situation in prison which he spent in the presence of the Baal Shem Tov and Maggid.
It is bordering on an insanity that some of you seem to be incapable of understanding that a person would suffer from having the derech in Avodas Hashem of his Rebbeim mocked, and you think that expressing that is somehow lacking in “Ahavas Yisroel.”
The whole reason the Alter Rebbe was imprisoned in the first place was because of the instigation and persecution of the misnagdim, it has nothing to do with some vandetta or abuse by the Czarist Government.