The irony about the "guns affect black people disproportionately" argument is that a majority of the gun crime against black people is committed by... black people.
All Homicide Victims: White-50.9%, Black-46.9%
All Homicide Offenders: White-45.8%, Black-52.2%
Gun Homicide Victims: White-47.2%, Black-50.9%
Gun Homicide Offenders: White-41.9%, Black-56.4%
Furthermore, the relationship between a murderer and victim is by and large very likely to be intraracial (ie: black-on-black or white-on-white violence). As per the DOJ, From 1976 to 2005, 86% of white victims were killed by whites and 94% of black victims were killed by blacks. IMO, statistics would seem indicate that if anyone might need to use self defense and the CD/SYG laws offering protections to such users - it is black persons.
The point I'm illustrating is this: Making up a minority of the population, blacks comprise a disproportionate amount of homicide victims. Furthermore when a black person is gunned down, it is almost always another black person pulling the trigger. This would tend to indicate that the SYG laws, given qualifying prerequisites, more often tend to offer an affirmative defense to a Black shooter - especially if the person shot was also black.
For interracial acquittal situations which you illustrate in your post, I would say that it's not the SYG laws that are the problem... it's the racist culture of the persons enforcing the law. SYG laws apply to everyone equally regardless of race. If the law is applied in a racially disproportionate manner, then the problem rests not with the law but the persons upholding it. IMO, that is not a good reason to get rid of a law designed to protect victims of assault.
For example, as Americans we have the right to be protected from illegal search and seizure. However black persons are far more commonly the victims of racial profiling and illegal search/seizure by police. This does not mean that we should throw away search and seizure laws due to racial disparity in application... instead we should demand punishment levied against racist authorities. SYG is no different.