Snobbery: it’s all over the book and it’s not going away. It’s no revelation that Proust is an elitist and a harshly judgmental one, but it’s something that evolves out of the social structuring, not an attitude that developed in isolation from the circumstances. In other words, the question in this book is not whether someone is a snob, but what kind of snob they are: Descriptive snobbery.
Some examples:
The Cottards. They aren’t snobs, but targets. They have no aesthetic sensibility.

M. and Mme Cottard, typical, in this respect, of the public, were incapable of finding, either in Vinteuil’s sonata or in Biche’s portraits, what constituted for them harmony in music or beauty in painting. It appeared to them, when the pianist played his sonata, as though he were striking at random from the piano a medley of notes which bore no relation to the musical forms to which they themselves were accustomed, and that the painter simply flung the colours at random on his canvases. When, in one of these, they were able to distinguish a human form, they always found it coarsened and vulgarised and devoid of truth, as though M. Biche had not known how the human shoulder was constructed, or that a woman’s hair was not ordinarily purple. (232)

What’s notable here is that the snobbery is based on Cottard’s utter failure of imagination. Their lack of appreciation for art is grounded in their inability to conceptualize the work in their head, which Proust considers primary (see Images).
Swann. Swann is eventually spat on by the Verdurins (see below) for descending into uncouth and non-social climbing behavior after becoming infatuated with Odette. Yet Proust passes a harsher judgment on him very late in “Swann in Love,” when Swann is unable to extend his view of Odette (idealized, and in his own personal experience) so that he realizes the extent of her decadent, adulterous, bisexual lifestyle:

Like many other men, Swann had a naturally lazy mind and lacked imagination. He knew perfectly well as a general truth that human life is full of contrasts, but in the case of each individual human being he imagined all that part of of his or her life with which he was not familiar as being identical with the part with which he was. (390)

(“Ah,” says Proust, “I shall do better!”) Is it fair to call this snobbery? Under the terms of the book, I think so. Swann is in a station (one of infatuation and idleness) that gives itself over to defects of perception and imaging, even if it allows him to perceive in brilliant clarity that brief passage of Vinteuil’s music. Marcel is in a station (a writer) where he thinks he’s doing much better, and who’s to say he isn’t? In this regard, there is a air of superiority.
The Verdurins. As hosts of many of the parties that Swann, Odette, and the rest of the gang attend, they are in the position of criticizing everyone while being (a) fairly immune, since they are incontrovertibly established (within their relatively low social circle), and (b) not much to speak of themselves, since they’re so petty and shallow:

“I don’t suppose it’s because our friend [Swann] believes she’s [Odette’s] virtuous,” M. Verdurin went on sarcastically. “And yet, you never know; he seems to think she’s intelligent. I don’t know whether you heard the way he lectured her the other evening about Vinteuil’s sonata. I’m devoted to Odette, but really?-to expound theories of aesthetics to her?-the man must be a prize idiot.” (248)

They’re really irritating. Their attitudes appear to flow from their position, which requires them to maintain a detached superiority from their guests. Hence passages like these.
(It’s been on my mind anyway, but this passage reminds me of the Hegelian master/slave analogy, where Hegel declares that the slave’s intervention for the master in doing any and all work for the master removes the master from the world and disconnects the master from all that is reality.)
Besides all that, M. Verdurin is incorrect, since Swann does have his issues with Odette. (see below)
Once Swann is well and truly obsessed, they make to cast him out. Swann thoughtlessly makes a slight verbal faux pas by praising the wrong person at one of the Verdurins’ parties. . .

Whereupon Mme Verdurin, realising that this one infidel would prevent her “little nucleus” from achieving complete unanimity, was unable to restrain herself, in her fury at the obstinacy of this wretch who could not see what anguish his words were causing her, from screaming at him from the depths of her tortured heart: “You may think so if you wish, but at least you needn’t say so to us.” (283)

The Hegel comparison doesn’t seem so off-base: the Verdurins (masters) need the backing and agreement of their guests (slaves) to maintain their position over the guests.
Swann and Odette. Swann initially can’t dismiss his low opinion of Odette’s brain, not as a judgment but as a fact:

Except when he asked her for Vinteuil’s little phrase instead of the Valse de Roses, Swann made no effort to induce her to play the things that he himself preferred, or, in literature any more than in music, to correct the manifold errors of her taste. He fully realised that she was not intelligent.
If, then, Swann tried to show her what artistic beauty consisted in, how one ought to appreciate poetry or painting, after a minute or two she would cease to listen, saying: “Yes . . . I never thought it would be like that.” And he felt that her disappointement was so great that he preferred to lie to her, assuring her that what he had said was nothing, that he had only touched the surface, that he had no time to go into it all properly, that there was more in it than that. (263)

This passage makes me far more sympathetic to elitism than I usually like to think I am. No one wants to admit that they feel agonizingly unable to explain the superiority of their tastes to some cretin that they’ve just met, and still everyone does, gets irritated, and then avoids the subject of their favorite work of art that the other dope couldn’t appreciate. Then they realize that Bush is still in the White House, chide themselves for being so shallow, and summon up newfound respect for the erstwhile cretin. Proust wouldn’t give; it’s close to the most important thing in the world for him.
For twelve pages or so Proust tracks how this feeling simmers and evolves in Swann, which is the subject for next time.