People don't understand you can't be pro-black and date out. If you are pro-black, you are committed to the advancement of black people. How.are you advancing the race by diluting it? When you marry someone you marry into their family, so now you have a bunch of white family members your allegiance is compromised.
You've now got a white wife/husband and biracial kids, who are likely to also marry out because they weren't raised seeing the importance of valuing black people, culture, and history because they also have white family, they split their time with.
You can still have Black pride/self-love but you are no longer pro-black. Your priorities is no longer there.
You can't teach/preach black beauty, black power, black economics and not put that into practice.