This question can be argued both ways.
On the one hand, you can argue that the existence of HBCUs fosters racism by separating whites and blacks. In this view, racism would be reduced if whites and blacks were put into contact with one another. Separating them gives each the opportunity to indulge in stereotyping about the other without having to confront the realities.
On the other hand, you can argue that separation at the college level is not a cause of racism. You can argue that HBCUs could actually reduce racism by reducing the stigmas attached to things like affirmative action. We can argue that sending blacks to “white” colleges is counterproductive when blacks end up there as part of affirmative action programs. That stigmatizes all blacks who attend the “white” colleges and adds to racism.
Thus, there are arguments to be made on both sides of this question.