To rant; to type noisily in a bombastic or turgid fashion with an eager, fixed attention on casting aspersion on a good name or reputation; to blacken.
John rushes to this website to Laura about Laura because he is relatively "small", diminutive, having only selfish, petty interests or narrow sympathies. He hides behind the guise of silly pseudonyms, as do the others who have followed and will follow in his cyber footsteps, and they, too, are just as shabby.
These 'small' ones wear hard hearts and are destitute of courage, character, or the backbone to simply Laura about Laura to Laura. Sadly, most will continue to color with black crayons, but given a Laura's magnanimous heart, I think you'd be surprised what might happen to yours should you give up your Laura in the shadows.