Attack negation/prevention - You can only 'tag out' a "Gladiator Beast" when it "attacks or is attacked", therefore, any Spell, Trap, or Monster Effect that lets you negate a monster attack would prevent the opponent from tagging out their "Gladiator Beasts".
Mekk-Knights have a bunch of cards to get rid of cards in particular columns (and of course, who could forget Infinite Impermanence?), making this 3000-damage direct attack super easy to pull off
When a Red-Eyes Monster declares an attack, this Fusion card allows you to take a Warrior Monster from the Graveyard and treat it as an Equip Card
[Edit] My guess is that Jirachi Prisms ability still works, because it states, before you put it in your hand, while Barbaracle is, instead of your hand. If Jirachi Prism heads for the bench, Barbaracle doesnt say instead of the bench, meaning it should go through
The interaction of these factors in complex ways determines a cards value