Every right must have boundaries, or it can not remain a right for any length of time. Your rights and my rights may be in conflict, and logically we cannot both exercise those rights 100% at the same time. For example, your right to smoke and my right to breath clean air may be in conflict, and someone's rights must give.
As an extension of that, it has long been legal precedent that spoken words can be grounds for murder. The clearest case is that of a hired killer. You make the call, establish contact, etc., and give instructions in a general sense (who, what general time, etc.). You need not even transfer money to be guilty of murder... you might promise payment after the murder and then refuse to pay - in that case, you never made any action in support of murder, but only your spoken word. Did you incite murder? The hired killer could have refused, on moral grounds, but the courts long ago decided that both parties are guilty. And for the life of me, I can't see any reason why I should not agree with them.
If you want to walk around talking about how much you hate blacks (insert any perceived group here) and how much you wish they would all die, that is your protected right. When you start telling your followers that they have to go out and kill blacks, you have crossed the line where your rights and others' rights meet. If you rant about how much you wish all blacks were dead, in a general way, and your followers take it upon themselves to commit murder... well, that's when the court cases get really interesting, and that's why our judicial system is organized such that cases can be judged on an individual basis.