Ubiquitin, the Gr”a’s chiddush was that a Yiddish minhag could become assur if adopted by goyim for avodah zarah (e.g. trees in their houses of worship).
The point here (I don’t know if this is what LF means) is that when a minhag has roots even merely hundreds of years ago, and is not only practiced, but advocated for and explained by great gedolim, to to assign the entire origin to a similar goyish minhag (especially in this case based on the flimsiest of evidence brought by someone with no track record) is arrogant, unwise, and an affront to the great people who did explain the reasoning and/or practice it without any reluctance.
Even if the Vilna Gaon himself were to have denounced it, at this point in history, even someone of litvish background should have the decency to respect an accepted Chassidish minhag even if he doesn’t practice it. Even if you disagree with that last sentence, the fact, though, is that we don’t have any such statement from the Gr”a.