Ah yes, the right arguing for "concrete statistical evidence". Have you taken a statistics course, at any point in your life?
That's an bar graph that fails to take into account any of the context that we should be using to talk about this issue.
For instance, if you had any grasp of science and statistics, you would know it's necessary to understand the process driving the deaths, rather than just the deaths themselves. There are far too many variables to control for to understand these deaths as a raw count (for instance, total interactions between black people compared to interactions between black people and white people, poverty, gun ownership, etc.).
It's pretty obvious why black people kill each other more than other groups in the United States. Black people in general have been living in perpetual poverty since slavery ended. It turns out, having the ruling race of the country you live in enslave you, let you free while still viewing you as subhuman, then denying you basic respect, jobs, business services can have a lasting impact on your culture. Most black parents today were alive when laws existed specifically targeted at keeping black people in poverty.
Oddly enough, when the Civil Rights act passed in the 1960's, black people didn't just receive billions of dollars for all the work they had done since they had been in the country. They were very, very poor, and people generally fucking hated them. They were also mostly living in inner cities (they had been forced there after slavery ended).
Many of them were able to get shitty jobs and maintain a basic living, and things were possibly starting to look up (even though, as I said, most people in the country thought of them as subhuman. Imagine walking around all day and being viewed that way, if you have the capability).
Now it also turns out that poverty is a bitch. Anyone living in poverty in America (or the world really) has a ton of issues that are difficult to comprehend unless you deal with them directly. Drugs become a popular outlet (for anyone in poverty). Violence is common.
Back to the main point, the CIA had a bunch of crack to sell in the 80s (as they had made deals with the Nicaraguan Contras), and they sold it to inner city drug lords. Guess who the market for the drugs were? Black people. You might think it's some big conspiracy, but seeing as how the average person fucking hated black people, we can easily guess that Reagan and the leader of the CIA hated black people, and were more than willing to sell them drugs to keep them down (or put them in jail). Most stupid people hate anyone different from them, and most people are stupid. So they created a crack epidemic within the black community (Capitalism is fucking awesome). This led to further violence, further poverty, mass incarceration. Did I mention that around the same time that black started using lots of drugs (whites have always used a ton of drugs), the U.S. thought that a War on Drugs was necessary, because idiots don't like black people and black people were doing more drugs. This wasn't any War, this was a war that specifically targeted black people (there are many statistics showing that black people are targeted at ridiculously increased rates for the exact same crimes/behavior as white people). So then a bunch of black men went to jail for mostly stupid reasons, because people are fucking idiots. Note that before the 80s, whites used drugs at higher rates than black people, but there was never a white men going to jail epidemic. Also, the sentence for crack was 3 times the sentence for cocaine, and guess which one is cheaper?
Long story short, ALL of these effects are still felt in black communities throughout the country. Many black children grow up without fathers, who were targeted at disproportionate rates compared to white drug using fathers. Many black children grow up in poverty, because their parents have a much harder time getting jobs, seeing as how most people still think they are inferior. Just having a "black sounding" name makes it much harder to get a job. Further, white people have generations of college experience, meaning they have the chance to make good money, they can then support their kids and give them better educations, their kids can go to college, make more money, and so on. Getting that process started when, as I've mentioned 10 times, people hate you and don't wish for you to succeed, is really difficult, and it's probably just starting now. There are more black people in college than ever before, and while they still are viewed as inferior by most of the people they attend college with, hopefully they can gain some momentum.
So, the "concrete statistical evidence" you see here, is a result of white racism towards black people in the United States, and it will be until the power balance is much more equal than it has ever been. Without much political or economic power for black rights movements (white supremacists have hold political office since the beginning of the U.S., and they've done everything they could to tilt the laws against black people), they're doing what they can to survive.
And we just keep pretending that black people kill each other because they hate each other.
Here's a source, there are many more but I'm too lazy, probably just go study history: http://nsarchive.gwu.edu/NSAEBB/NSAEBB113/north06.pdf