Kaido spent 33 years raising a massive army
All that hard work, only for Queen to open his big mouth and make them switch sides
What the fuck Oda? This is a new low of PIS
To be fair, the ones he said it to were all the more useless type of fodder. They are, as far as Queen is concerned, about to die anyway, and they were clearly acting rather rebellious already. The fact that they were questioning Queen at that point was evidence that the straw hats had already broken their spirits.
But, you still don't seem to understand the Beast Pirate's main Mode of Operation: the Beast Pirates are a group that try to work by crushing the spirits of those beneath them, allies or enemies, until they feel so helpless and put down that they give entirely into demands.
Queen's speech might've been the sort of thing which might cause somebody to switch sides, but it also might be the sort of thing which causes severe disillusionment, resulting in the Beast Pirate fodder fighting more vigorously for the winning side, which, looking at the numbers, is still clearly the Beast Pirates, or to turn rogue and fight entirely for themselves, which would also be a favorable outcome for the Queen, since then they'd go after Chopper who might still hold the antidote.
If the Strawhat Pirates weren't so morally immaculate that the Beast Pirate Fodder decided to trust them anyway, what Queen did would've been an objectively good tactical decision.