Forest have every right to be apoplectic about that third penalty decision, I can't fathom how VAR didn't give it.
Where they've crossed the line is publicly calling the official's integrity into account. That doesn't seem like a sensible thing for a supposedly professional outfit to do.
That being said, I'd be genuinely surprised if there's a single impartial person in the country with eyes who would (non jokingly) claim it wasn't a foul. So to be fair to them, either the VAR assistant was biased in their decision making, or they're so severely incompetent at their job that this decision is grounds for instant dismissal from their position and they should never referee professionally again.
There's no excuse for getting that so incredibly wrong with the luxury of replays. I'm baffled.