You would be hard pushed to argue that the Australian aborigines brought enough force to bear to abolish white supremacy, or indeed that black minorities in the UK forced the ruling class to give concessions. In fact most liberalisation seems to have happened where the opposition slackened; when the ruling class were challenged, racial oppression was cranked up. The US that countenanced a black president was not one that was fending off militant challenges. Even in South Africa, the ruling elite their took advantage of the disorientation of the S.A.C.P. after 1991 to get the ANC to commit to the continuation of the market economy.
It seems to me that reformist parties were the vehicle that introduced nationalist sentiments into the working class movement in Europe. In Britain, it was the Labour Party's national recovery strategies that made nationalism attractive to working class supporters. It was the official trade union movement that operated the 'last in first out' model of white preference in hiring for much of the twentieth century. The growth in white identification was closely related to the extension of democracy. And with the decline of classic reformism, racial identification has become a lot less strongly rooted (take the growth of inter-racial couples in the UK as an example).