Rap music hit the Top 40 in 1979, but took a new turn around 25 years ago in early 1988 with the introduction of crime-glorifying gangsta rap, which arrived almost simultaneously with crack and an increase in the black youth homicide rate. Black homicide offenders had averaged about 10,000 per year in 1983-87, but then averaged about 15,000  per year from 1990-94.
The general theme of gangsta rap is that to be authentic, black males should follow a code of conduct that increases their likelihood of murdering other black males.
The Rev. Al Sharpton hates gangsta rap  and intermittently crusades against it. I wouldn't be surprised that if Sharpton could make a decent living as an anti-gangsta rap advocate, that that would be his first choice of cause. But beyond the Tyler Perry audience of older black church ladies, there's nobody terribly interested in supporting advocacy on this topic.
To younger white people, well, of course black people make hit songs about poppin' a cap in each other. It's just a thing they do. Haven't they always done this?
It's difficult to explain to anybody younger than a certain age that black people never used to make hit records about such a thing. The closest parallel might be blues songs like Jimi Hendrix's "Hey Joe " about shooting your messing around woman down, but they generally were played as tragedy, not advice.
Has anybody's career ever suffered for having been a gangsta rapper? Ice Cube stars in family movies now and Ice T fights crime on one of the Law & Order shows. How much trouble have media companies gotten into over the years for purveying gangsta rap? A little, but not much.
So, within an order of magnitude, how many homicides could reasonably be attributed to gangsta rap over the last quarter of a century? Let's assume that it has zero affect on non-blacks. Assume blacks commit half of all homicides, and there have been maybe 16,000 total homicides per year over the last 25 years, or 8,000 per year by blacks.
Now, what percentage of black homicides are due to the existence of a major genre of catchy rhymes advocating thug life?
It's pretty much impossible do disentangle factors with confidence, but I'll say, 5%. How do I know that? I don't, but it seems more plausible than 50% or 0.5%. So, 5% of 8,000 is 400 deaths per year.
Over 25 years, that sums up to 10,000 murders.