That's not nice to say such Loshon Hara about a poster.
I do not know to whome you refer.
But if you WARN jews about a person. That is not lashon Harah. It is infact, something else, and it is an obligation.
A friend, a great scholar on paltalk, said
to paraphrase him, according to my understanding
rechilut.. is passing on information that helps another person. a warning.
it is permissable when trying to save others from falling into a trap.
It is not lashon harah.
And by that reasoning, he would warn about shmuley boteach, for saying such things as judaism is not just for jews.. he is a rabbi teaching heresy and that is dangerous.
The friend is not a kahanist.. But he is a great scholar. He is so frum, I think he considers Rabbi Steinsaltz to be a heretic!
---ADDED CORRECTION-----
I just spoke to him directly. He does not consider him a heretic.
But he considers him very wrong, in setting up the "sanhedrin"
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