This one kind of bugs me, homicide rate per 100k in the US is 6.3.
So basically ever group below 6 is in sets of 2, then as soon as it gets to 6 they group by 4 twice and then infinite.
So this has the effect of making it look like the USA has the same homicide rate as countries that are almost 4 points higher, or what would have been two entire color groups previously, and making it look like the US is in the median for the whole world (after all there's only two groups before and two groups after).
Whereas if they had kept to the 2 points per color rule the US would have only just barely been in the 4th group of 31 (El Salvador sitting at 61.8).
Basically, the image was absolutely designed to make it look like the US has a worse homicide rate in comparison to the rest of the world than it really does.