[WS:] Whether it is viewed as "embarrassment" depends on where one sits, politically.
One of the most interesting aspects of the American society is that it is pretty much devoid of politics in the traditional sense - as tactical pursuits of power for the sake of wielding power. Instead, the traditional polity bifurcates into two adjacent areas - business and religion. Or more precisely, politics is either an instrument of money making or - if it does not fit that mode - it becomes a religious ritual.
One consequence of this is that outright rejection of the marriage between money and politics almost invariably movers one into the realm of religion. This is what happened to the left-of-the center here. It bifurcated into "liberals" defending certain occupational or regional interests (teachers, manual labor, public services, urban population, etc.) in the political arena (mainly through the Democrat party) and "radicals" who left the political arena for religious pursuits, such as interpretation of the scriptures, incantations, or observance of rituals (e.g. street demos.) This is demonstrated, inter alia, by the centrality of scripture exegesis (e.g. endless quotations from Marx, Engles, Lenin etc.) and concepts such as "classless society" "end of work" or "abolishing the wage system" in the radical discourse. They are secular versions of the religious notion of "heaven." They are all words that have no empirical meaning by definition - as the are all constructed by simple negation of empirical reality as we know it - all they have is emotive connotations of the state of ultimate satiation, bliss, ecstasy, sexual gratification, and general happiness.
The only exception from this business/religion bifurcation of politics in the Etats Unis is what Corey Robin describes as reactionary activists - they pursue politics for the sake of power rather than just pecuniary gains. Although pecuniary gains typically follow their political action, I buy Robin's argument that this is not what primarily motivates these guys. Their primary motivation is power and devising clever stratagems to gain it - and this is why they stand head and shoulders above both, the political mainstream (Democrats, liberals, and centrist Republicans) and the religiously radical left in the Etats Unis.
With that in mind - being a liberal is a reason of "embarrassment" and scorn only for the religiously radical left and the tactical reactionary activists, albeit for different reasons. For the religiously radical left, liberals are the part of the politics-as-business which the the radicals reject, but they also occupy areas that are adjacent to that claimed by the radicals. This poses a danger for the radical identity. Nobody will confuse, say, a centrist Republican with a radical, but the demarcation line between liberals and radicals is blurred, and taking one for another is more likely. This calls for radical measures of turf demarcation - of which scorn and vocal denunciations are an important part.
Reactionary activists, otho, scorn liberals for tactical reasons. Unlike radicals, they do not feel threatened by liberals in any way - and this is precisely what makes liberals useful for reactionary tactic. The success of reactionary tactic depends on creating the sense of fear and endangerment, which in turn calls for "defensive" measures entailed in reactionary political moves. However, the manufactured danger cannot be real, for that poses the risk of defeat.
It must be phony but it must look scary. Liberals serve that function rather well - they are not powerful to begin with, and they are not very combative, so the chance of them inflicting a serious damage on reactionaries is small. However, their views can easily be demonized by rather crude propaganda portraying them as out of whack with what most red blooded 'Muricans consider "common sense."
But other than these two factions, being liberal is not a reason of scorn at all. Centrist Republicans or conservative Democrats may disagree with them, but they do not scorn them - they have no reason to.
Wojtek