Dana White hates the idea of a costume party before a big fight -- which is why he won't allow UFC fighters to play dress-up like Deontay Wilder did at the Tyson Fury fight.
The UFC honcho thinks Deontay's decision to rock a 45-pound costume during his ring walk was ill-informed ... but says ya can't blame the whole loss on the outfit -- give credit to Fury!
"I think there's a lot to it. Fury looked awesome," White says ... "Fury fought a perfect fight.