For your quotes, try Chapter 3 of The Communist Manifesto

Owing to their historical position, it became the vocation of the aristocracies of France and England to write pamphlets against modern bourgeois society. In the French Revolution of July 1830, and in the English reform agitation[A], these aristocracies again succumbed to the hateful upstart. Thenceforth, a serious political struggle was altogether out of the question. A literary battle alone remained possible…

In order to arouse sympathy, the aristocracy was obliged to lose sight, apparently, of its own interests, and to formulate their indictment against the bourgeoisie in the interest of the exploited working class alone. Thus, the aristocracy took their revenge by singing lampoons on their new masters and whispering in his ears sinister prophesies of coming catastrophe.

In this way arose feudal Socialism: half lamentation, half lampoon; half an echo of the past, half menace of the future; at times, by its bitter, witty and incisive criticism, striking the bourgeoisie to the very heart’s core; but always ludicrous in its effect, through total incapacity to comprehend the march of modern history. The aristocracy, in order to rally the people to them, waved the proletarian alms-bag in front for a banner. But the people, so often as it joined them, saw on their hindquarters the old feudal coats of arms, and deserted with loud and irreverent laughter.

It is interesting to compare this with the section Ruling Class and Ruling Ideas in part I.B of The German Ideology. The following isn’t what you were asking for, and instead discusses how a class, when contending for dominance, must express its own ruling ideas and interests as the universal ideas and interests of all classes, i.e. of “all of society”. In actuality those ideas (of the bourgeoisie, aristocrats, etc.) are not truly universal though. This is written in the context of a new class, such as bourgeoisie, striking for dominance in an old order, such as the feudal order. But when the aristocrats try to fight back and maintain power, they will still aim for the same tactic. To express their ideas and freedoms as universal freedoms for the proletariat and as presenting themselves as guardians against the nefarious and harmful bourgeoisie, as explained above in The Communist Manifesto. Quoting from The German Ideology:

For each new class which puts itself in the place of one ruling before it, is compelled, merely in order to carry through its aim, to represent its interest as the common interest of all the members of society, that is, expressed in ideal form: it has to give its ideas the form of universality, and represent them as the only rational, universally valid ones. The class making a revolution appears from the very start, if only because it is opposed to a class, not as a class but as the representative of the whole of society; it appears as the whole mass of society confronting the one ruling class.

It can do this because, to start with, its interest really is more connected with the common interest of all other non-ruling classes, because under the pressure of hitherto existing conditions its interest has not yet been able to develop as the particular interest of a particular class. Its victory, therefore, benefits also many individuals of the other classes which are not winning a dominant position, but only insofar as it now puts these individuals in a position to raise themselves into the ruling class.

When the French bourgeoisie overthrew the power of the aristocracy, it thereby made it possible for many proletarians to raise themselves above the proletariat, but only insofar as they become bourgeois. Every new class, therefore, achieves its hegemony only on a broader basis than that of the class ruling previously, whereas the opposition of the non-ruling class against the new ruling class later develops all the more sharply and profoundly.