To suggest BLM wants to kill all white cops is right wing rhetoric dribble.  What they want is equal treatment from cops when being pulled over, or for having a legal gun, or for, you know, just walking the streets.
Yes, there ARE bad eggs in that group, just like there are bad eggs in nearly every group - but that group was not founded on "kill all white cops".  The core concept of that group is to get equal treatment.  Whereas the core concept of White Nationalists is the elimination of anyone who does not look like them. 
You suggesting that BLM is "the same" as White Nationalists actually gives more power to White Nationalists because you are equating them to a movement towards equality.  Which they are anything but that.  To prove my point, how many black people do you see joining the White Nationalists?  Where as BLM is not exclusive to black people, and many people who support that movement are in fact white, and latino, and gay, and straight, and jewish and muslim.