Richard Sherman is America’s ranter of the moment after his inspired, misguided, comical, cruel verbal assault of 49ers receiver Michael Crabtree.

Sherman has been attacked with fervor and defended with more fervor. He’s risen from beloved player in Seattle, where he stars as a cornerback for the Seahawks, to cult hero in America. All because of a 20-second rant as he stood beside Erin Andrews.

He’s even drawn comparisons to boxer Muhammad Ali, the once and forever emperor of smack.

A little advice, Mr. Sherman, as you and your mouth march forward.

Be careful. Your words carry immense power. Yes, the might to transform you to instant celebrity, but also the might to injure. Words spoken, even in jest, can create deep, lasting enmity.

Ali, one of Sherman’s heroes, knew all about the power of words. He sold tickets and lifted himself to a 20th-century giant with his funny, biting, insightful and inciteful words, but he failed to see the boundaries of his trash talk. He went too far in his wicked abuse of fellow warrior Joe Frazier.

Frazier, who died of liver cancer in 2012, never forgave Ali. Smoking Joe had reason for this hatred. To sell three fights, and to rattle Frazier, Ali created a caricature of a brutal yet sensitive heavyweight.

Ali said Frazier looked so ghastly his face should be donated to the bureau of wildlife. While sitting beside Howard Cosell, Ali called Frazier an “ugly, dumb gorilla.”

The words shook Frazier, who never released a seething hatred for his nemesis. I witnessed this hatred in 1995 while interviewing Frazier as we walked along the streets in upstate New York. I kept asking Frazier about Ali, and Frazier kept refusing to speak his name.

Frazier would talk about any other subject, including the night George Foreman beat him silly in Jamaica. Smoking Joe even sang to me between bites of a hamburger garnished with green and red peppers. I can still see those green and red specks gleaming in the gaps of Frazier’s teeth.

He would not speak Ali’s name.

When watching Ali ignite the Olympic flame at the Atlanta Games in 1996, a year after my conversation with Frazier, I was overwhelmed. Ali traveled such a long and winding road, climbing from poverty in segregated Louisville to the mountaintop of glory. He tangled with racism and Uncle Sam and snarling heavyweights. And he triumphed. What a moment in American history.

Meanwhile, Frazier pondered dark, vengeful thoughts. He wished he were standing beside Ali. Why? So he could push Ali into the flames. Smoking Joe wanted to see a smoking Ali.

Ali employed his mouth as a weapon against dozens of fighters, and most laughed along with him. When mocking his opponents, he promoted the utter wonderfulness of Ali, but also sought to sell tickets. He wanted to add to his wealth and his opponent’s wealth.

Frazier did not know. He despised the man who talked so frequently and so loudly. I have a strong feeling Crabtree harbors the same scorn for Sherman.

What’s puzzled me for the past 10 days is the unquestioning wave of support surrounding Sherman. I keep hearing about his Stanford degree and his determined rise from the fierce streets of Compton, Calif., and his devotion to his parents.

But what about his actual words? What about the way he demeaned and ridiculed Crabtree while the football world listened? Sherman, the ever-striving man, is easy to admire. Sherman, the repulsive talker, is impossible to embrace.

Sherman could spend his entire career talking loudly, making fun of those enemy receivers. And his fame, along with his infamy, will just keep multiplying. America loves its loudmouths.

But there’s a price for verbal cruelty, a price that still follows Ali.

In 1996, Ali gazed at a roaring Olympic flame. This was his ultimate moment of triumph, but even as he stood in the light he must have known a proud man he had wronged wanted to see him in flames.