Just like yashke ymach shemo, kook yemach shemo was a liar and kofer in the Torah. His evil teachings were well documented in his life, with numerous gedolim calling him out and putting his decrepit writing in cherem. He himself was forced to admit that he made up a new torah when famously confronted by – lehavdil – the Gerrer Rebbe ztz”l, but despite kook’s promises to retract his egregious corruption of judaism from his printed books, he never did.
Kook was widely mocked by Gedolim in his life, calling him “the fake prophet”. He was called a “rushe gumir” by Rav Elchonon Wasserman ztz”l. And tzadikim since then have continued to say “yimach shemo” when mentioning him and demanding his books be burned or at least thrown in the garbage like any other book of heresy