I think that "white backlash" and "gangster gratification" are two different things. The first one is a popular emotion, whereas the other one is a form of expressing that emotion. As you observed it yourself, the "white backlash" used to be expressed in the form of "law and order" - which regardless of its racist innuendos, was an essentially a mainstream rational discourse. Everyone supports law and order, nobody supports lawlessness and mayhem, the only disagreement is which government department should be in charge of creating that law and order: Department of Public Welfare/Education or Department of Corrections. As former Baltimore mayor Kurt Schmoke used to say, a policemen is a social worker with a gun.
The message introduced by gangsta rappers, video games and Bush administration is a very different one, however. It still banks on pre-existing emotions (dissatisfaction with the status quo) but it does not asks for justice, law and order any more, but instead asks to unleash mayhem to get whatever fuck we want. This is the anti-thesis of law and order, the rejection of civil society as we know it. It is not social work with or without a gun - it is "me" with a gun against everyone else - either in the streets or in the world.
The spread of gangsta rap - which btw was first popularized by white college stations not by Black stations that played mostly the "conventional" Black genres was the first signal sent by the corporate America that the social contract as we know is over, it is war of all against all, and let the strongest individual win and take all the spoils. I would venture as far as saying that the fact that gangsta rap started as a "black" genre is in itself symptomatic of the US racism. The white bosses used blacks to do the dirty work for them - inculcate the public with the nasty and unpleasant message that social contract is over - individualism, greed, hate, violence and race to the bottom are in.
Of course, I am not arguing that gangsta rap is the cause of all that change - its emergence and popularity is merely a signal of the end of an era. The causes lie much deeper - some of it is undoubtedly elite manipulations and inculcation with individualistic values, but I think most of it is structural - democracy turning into a mob rule about which so many writers, from Aristotle to de Tocqueville, to Mencken and to Hofstadter warned us about.
I absolutely agree with you that the left and liberals cannot emulate that game without betraying their most fundamental principles - but I am also aware that this is the game being played right now, so the only choices that we have is to either "bark with the pack or be lost" (as HL Mencken aptly said). Which means that things will continue getting worse before they start getting any better.
Another caveat - this is not to imply that this is a result of "human nature" or similar nonsense. I do not believe in a fixed "human nature" - most people by nature are capable of both good and bad things, and it is social interaction, situations, and institutions that release the potential for each. But interactions and institutions create path dependencies which must run their course once their set it. You cannot simply quit and start doing something else in the middle of the game - you need to either play along or leave.
Wojtek