Martin Eden's view of Ruth is initially very positive, although the same cannot be said of his opinion of the upper-middle-class stratum from which she comes.
Whatever Martin's initial feelings for Ruth, there's no doubt that he feels a certain degree of animosity towards her class. Martin feels completely out of his depth in the Morse household, being as how he hails from a lower-class social background. Blithely unaware of the social graces, Martin cannot help but give away his lowly origins, and this makes him feel inferior. As indeed does the snobbish contempt expressed towards him by Ruth's family.
Even so, it's striking that Martin, in regarding Ruth as the very embodiment of pure womanhood, demonstrates an ability to forget about social class, albeit briefly, in perceiving another human being's special qualities. But in the event, and despite the initial strength of Martin's feelings towards Ruth, the huge social gulf that separates them from one another cannot be closed, and Martin understandably feels resentful as a consequence.
The significance of Martin's view of the middle classes is that it provides in his mind an explanation of why he hasn't achieved the recognition he thinks he deserves. Although he's become a successful writer, whose stories are now in high demand by magazines, he realizes that he's simply flavor of the month and that he'll soon lapse into obscurity once fashions have changed. For this, he blames the shallowness of the bourgeoisie.
Over time, Martin's attitude towards Ruth changes, as he comes to see her as representative of her class, with all the negative consequences that that entails.