The Grush Lieberman never once denied any of the ikkarei haemunah.
And if he was so bad, than how did he maintain a kesher with Rav Soloveitchik, the Lubavitcher Rebbe, Rav Hutner, and scores of other gedolim?
His Tosefta Kifeshuta and Yerushalmi Kifeshuta are found on the shelves of any serious talmid chacham and are found in the libraries of many yeshivot.
I am fortunate to have many of his students as teachers.