Dear Avira,
The majority of the Rebbes were clamoring to speak with him. He was in touch with Gedolim from all parts of the Diaspora. He had some correspondence with Rav Moshe. Unlike some others, Rav Moshe did not have to explain him things. He was Ari Shebechabura by Rav Weinberg in Berlin. The Lakwood Yeshivaliet would go to his farbreingins because they liked his lomdus.
If your position would be that he was a flawed human being, you could get away with that. (Unless the mods don’t want that debate.) If you think he was mistaken or delusional about certain things, very few people can assert the truth, so you’ll win the debate. But to say he wasn’t a gaon when his genius blew away some of his greatest detractors and he has thousands of profound and deep writings, makes you lose all the debates. From your ability to admit the truth, he could easily be alive and sitting right next to you.
I wish you would take this advice, because once you wrap your head around how great he was according to the yeshivishe standards of a gadol you would have a much easier time debating Chabad. When you write everything off, you lose. This is the primary reason that Chabad increased it’s dominance since the Rebbe died.