Did Barack Obama stop racism and how?

No. Nor is it likely he will be able to. No one person-- not even a president-- can stop racism. Barack Obama's election as the first black president in US history was certainly an important step, and it is encouraging to note that a large number of white people voted for him. But sadly, there are still many people who would never vote for a black person (whether a Republican or a Democrat); and some of those people do still hold on to racist attitudes. The good news is that there are fewer of them than there were, let's say, 30 years ago, but they do still exist.

Barack and Michelle Obama are important role models, since they are a successful black couple with Excellent educations and a beautiful family; but the fact that they are in the White House will not eliminate racism. It will take an ongoing effort by schools, religious institutions, and the public at large to speak out against the old racist attitudes that are still engrained in some corners of our society. Fortunately, there is no evidence that anyone is born prejudiced: prejudice must be learned. So perhaps the next generation of kids who are growing up with a black president will think such things are perfectly normal, and they will reject the racist attitudes they may still hear from some older people. Meanwhile, there are laws that criminalize certain racist behaviors, but even the best laws cannot eradicate bigoted attitudes. Only time, and generational change, can decrease racism in our society.