Why won't Republican leaders take any sort of actionable stand against Greene? Because to do so would run the risk of putting them at odds with the base of the GOP and its leader -- former President Donald Trump.
See, Greene (like Florida's Matt Gaetz and North Carolina's Madison Cawthorn, among others) are the offspring of Trump's political revolution. They seek out controversy. They say wild -- and wildly offensive -- things to "own the libs." And the base responds -- sending millions of dollars their way -- as they are further fêted by conservative media outlets for their anti-woke messaging.
Which makes the likes of McCarthy very nervous. Because he wants to be speaker if Republicans win back the House next November, and he knows the only way he does it is with the base liking (if not loving) him. And so, he sits silently when words (and actions) are very necessary.
The question McCarthy and his fellow Republican leaders have to ask themselves at this point is this: Is it worth leading a party that stands for nothing outside of total and utter loyalty to a single man -- and which is unwilling to strongly condemn clear intolerance and ignorance? Is leading that empty shell leadership at all?