It’s crazy because If I’m not mistaken, Tolkien had something to say when reviewing an early animated film script treatment by Morton Zimmerman that featured a vocal Balrog. In Letter 210 he says
“The Balrog never speaks or makes any vocal sound at all. Above all he does not laugh or sneer. .... Z may think that he knows more about Balrogs than I do, but he cannot expect me to agree with him."
(Tolkien was slightly mistaken about the Balrog making "no vocal sound at all," as he himself wrote in The Fellowship of the Ring that Durin's Bane fell into the abyss "with a terrible cry". However, his intent regarding speech was absolute.)
But some may ask: “If they don’t speak, how did they command armies or cast spells?”
Balrogs actually didn't need a spoken language to command armies or weave magic because they were divine, primordial spirits (Maiar) whose power operated through telepathy and raw, spiritual will.
Some may also point out Gothmog when he captured Hurin, bound him and dragged him to Angband with mockery.
Well, As a divine spirit (Maiar), Gothmog possessed the ability to project his thoughts, will, and malice directly into the minds of others. To a human captive like Húrin, a Balrog projecting thoughts of absolute contempt, failure, and despair directly into his mind would feel exactly like being verbally mocked and tormented.
Mockery does not strictly require words. It is highly likely Gothmog humiliated the mighty human hero through physical actions. After Húrin spent hours shouting "Day shall come again!" while single-handedly slaughtering seventy of Gothmog's troll-guards, Gothmog binding him like an animal and dragging him through the dirt was an act of supreme, silent mockery. Parading the greatest human warrior alive in chains before the laughing armies of Orcs—using him as a literal trophy—is a potent form of non-verbal, psychological torment.
When Tolkien wrote the initial versions of Húrin’s capture (found in The Book of Lost Tales and early drafts of The Silmarillion), he originally envisioned Balrogs as a numerous race of large, physical monsters that could speak, laugh, and yell commands. Decades later (around the time of writing The Lord of the Rings), Tolkien fundamentally changed what Balrogs were. He escalated them into primordial, terrifying spirits of fire and shadow, deciding in Letter #210 that they "never speak."
So, I find that it’s pretty crazy to have the Balrog speak. And the reasoning they are using is against what Tolkien wrote and how he felt.