What is the significance of Slackbridge as a character and the overall quotes he says to the thematic concerns of the novel?

Slackbridge is a trade union organizer who tirelessly campaigns to recruit union members and thereby improve the working conditions at Bounderby’s factory. Charles Dickens portrays him as an unscrupulous zealot. Slackbridge’s character and actions fits well with the novel’s overall theme of the changing attitudes to the horrific labor conditions in 19th-century England. In the 1850s, strikes crippled some of the largest mills; one was the Preston strike in Lancashire, which Dickens observed firsthand.
The conflicts arise both in Slackbridge’s goals and his methods. In his passion for the unionization cause, he rejects the validity of any challenges and takes down his opponents. His vigorous oration in the hall meetings aims to inspire the workers to action, as he calls to his “fellow-sufferers, and fellow-workmen, and fellow-men . . . [to] rally round one another as One united power.” Through the union, they can free themselves of “the galling yoke of tyrants on your necks and the iron foot of despotism. . . .” Throughout this speech, Slackbridge calls attention to Bounderby’s notice condemning Stephen Blackpool, a weaver who has been driven out of the factory. While he refers to Blackpool’s dishonesty as a reason for leaving, his refusal to support the union had led Slackbridge himself to discredit him.
http://dickens.stanford.edu/hard/issue6_gloss.html