If you are in business on your own where you have an advertising website, you are under no obligation to advertise for every person or company that may want you to do work for them.You are free to pick and choose who you want to represent. For example, attorneys are not obligated to represent every possible client that comes into his or her office. The same should hold true for what you want to do as well. You cannot refuse to do work for someone based upon discriminatory motive however.