"never expected to hear a coxcomb ask two hundred guineas for flinging a pot of paint in the public's face"
Whistler, on the other hand, took a very different route to receive this title. His journey seeking what he believed to be justice is very important in seeing how critical (ha, get it, critic-al, hahahaha wow I need to get a life) the art critic is to the process of changing art movements.
Critics are instruments of change through the fact that their judgments and statements affect how the public views artwork, whether they are conscious of it or not. Also, they can even determine whether or not a certain art movement will be successful and prosperous, just by giving their professional opinion on the artwork coming out of the movement. However, their goal is not always realized; sometimes the result is the opposite of what the critic wanted to happen. As a general example, a critic could create so much publicity for an art movement, even if it is negative in nature, that it catches the attention of more well-known artists who may be intrigued by the new styles of work being created. This, in turn, allows the movement to grow in size and in technique and content.
Art thrives under pressure. Intense emotions breed works of beauty, and works that simply convey the feelings better than any amount of words could.
Personally, I think that it's hard to side with either person, because each had an important cause to defend: Whistler, his dignity and the reputation of his painting, and Ruskin, his reputation as a critic and his ability to continue and make income. The relationship between the artist and the critic can be seen as a symbiotic one; each depends on the other to survive and mature.