As Martin Luther King said in many of his speeches, most famously at the March on Washington, he was fighting to redeem a promise that the United States had made at its founding. This promise was that all people were equal, and ought to be treated that way under law. So I would argue that it is almost impossible to argue that the things King was fighting for were not important. Part of his appeal at the time and since is the way that his rhetoric appeals to American values, contrasting the realities of racism and racial discrimination with the things that Americans want to believe about themselves. Moreover, while King has been made "safe" by decades of veneration, many of the things he argued for, especially late in his life, are controversial (but no less important) today. He vehemently opposed the Vietnam War, he advocated for a stronger social safety net and a welfare state, and he fought for workers' rights, including those of white workers. It was a sanitation workers' strike, in fact, that brought him to Memphis in April of 1968, when he was assassinated. In short, the battles King fought were battles over the soul of America, and whether it could live up to its promises. They were, and are, important to say the least.