There is an argument to be made that carrying a knife should not be a crime for anyone, and that we all have a right to carry a knife to protect ourselves or even use a tool.
But lets accept for a moment that reducing the number of knives on the street reduces violence and protects innocent people. If you accept that premise, then you have to say it's beneficial to society that the police remove as many knives as possible: whenever someone gets arrested for a knife violation it's a good thing, regardless of their skin colour.
And given that we have limited enforcement resources, we should focus most in those areas with the most knife crime victims. So while i accept everything you relayed in your post, the proper conclusion would change quite a bit if there are many more victims of knife crime in the black neighbourhoods... I do not know if that is the case, and i'm not implying the answer is more likely one way or the other.
But if in fact more people are getting stabbed or robbed at knife point in black neighbourhoods and you accept that knife laws are good in general, then it's good that such laws are more strictly enforced in that area, to help protect all the innocent people in that area who might fall victim.
And this principle really is colorblind. For instance many people speed in their cars everywhere, but we should more heavily enforce speed limits near high traffic and pedestrian areas and locations where accidents keep happening.
Now, maybe the rate of knife crime is worse in white neighbourhoods, in which case it really is a miscarriage of justice that more black men are getting charged for illegal blades. But I don't think you can say one way or the other without knowing and considering that statistic.