There is no contradiction. That 3 million number is bad, but it is still better than the 1.5 million number because of the methods used. Because prisoners didn't go down under Republicans. The prison system didn't get better under Republicans. Police killings didn't get better under Republicans. Like, I know it's gauche to try to compare hurt, but I do not see any Republicans calling for a rehabilitation system instead of a punitive system, but I do see some Democrats call for it, even if very few.
Like, it's sort of like telling me to pick between 1000 thefts being committed vs 100 murders, and, like, yeah, obviously I'll take 1000 thefts over the murders. I don't want either, but I have two fucking choices.
Which would you pick? Remember, there's quantitatively less crimes with the murders! Oh, you didn't pick? That just means someone else gets to pick for you.