mdd1: “there was one Chassidishe Rebbe (not a contemporary one) who held that Zimri was right in what he did with Kozbi”
I can only assume that you’re referring to the famous piece in Mei Hashilo’ach of the Izhbitzer Rebbe z”l which explains that what Zimri did was due to his understanding of Torah. Nonetheless, the Mei Hashilo’ach says that Zimri was mistaken, and not right as you have written. See the first piece in parshas Pinchas.
If I am wrong in my assumption, and you are referring to a different rebbe, please provide a source.