Rabbi Wallerstein’s reasoning, if I’ve got this right, is because they encourage people to leave yiddishkeit.
His shiur last week (heard on Torah Anytime) dealt with the signs of Moshiach’s arrival from the gemora at the end of Sotah. He said that the Footsteps people didn’t realise that Ikvesah d’Meshicha is translated as Footsteps of Moshiach.