There are many references to Garrison in Hubbard's books. The reference posted about the Boston incident seemed to be a close paralell -- but this description from Hubbard himself seems to make it clear that Hubbard's good man was William Lloyd Garrison the American anti-slavery activiist.

From
Little Journeys to the Homes of the Great, Volume 7
Little Journeys to the Homes of Eminent Orators
WENDELL PHILLIPS

"The disappearance of the women seemed to heighten the confusion: there
were stones thrown, sounds of breaking glass, a crash on the stairway,
and down the narrow passage, with yells of triumph, came a crowd of men,
half-dragging a prisoner, a rope around his waist, his arms pinioned.
The man's face was white, his clothing disheveled and torn. His
resistance was passive--no word of entreaty or explanation escaped his
lips. A sudden jerk on the rope from the hundred hands that clutched it
threw the man off his feet--he fell headlong, his face struck the stones
of the pavement, and he was dragged for twenty yards. The crowd grabbed
at him and lifted him to his feet--blood dripped from his face, his hat
was gone, his coat, vest and shirt were in shreds. The man spoke no
word.

"That's him--Garrison, the damned abolitionist!" The words arose above
the din and surge of the mob: "Kill him! Hang him!"

Phillips saw the colonel of his militia regiment, and seizing him by the
arm, said, "Order out the men to put down this riot!"

"Fool!" said the Colonel, "don't you see our men are in this crowd!"

"Then order them into columns, and we will protect this man."

"I never give orders unless I know they will be obeyed. Besides, this
man Garrison is a rioter himself--he opposes the government."

"But, do we uphold mob-law--here, in Boston!"

"Don't blame me--I haven't anything to do with this business. I tell
you, if this man Garrison had minded his own affairs, this scene would
never have occurred."

"And those women?"

"Oh, they are members of the Anti-Slavery Society. It was their holding
the meeting that made the trouble. The children followed them, hooting
them through the streets!"

"Children?"

"Yes; you know children repeat what they hear at home--they echo the
thoughts of their elders. The children hooted them, then some one threw
a stone through a window. A crowd gathered, and here you are!"

The Colonel shook himself loose from the lawyer and followed the mob.
The Mayor's counsel prevailed: "Give the prisoner to me--I will see that
he is punished!"

And so he was dragged to the City Hall and there locked up.

The crowd lingered, then thinned out. The shouts grew less, and soon the
police were able to rout the loiterers.

The young lawyer went back to his law-office, but not to study. The law
looked different to him now--the whole legal aspect of things had
changed in an hour.

It was a pivotal point."