When the black lives matter movement whipped people up into a frenzy based on absurd "victims" (Treyvon Martin, Michael Brown, etc.) and stories and numbers that were misleading at best to downright false ("hands up don't shoot!) they promoted this hateful culture that has now led to officers being murdered. Liberals and liberal politicians embraced BLM. They encouraged it. They participated in it. Liberals don't get to just wash the blood off your hands now and say "gee this is really sad. Hey now, this isn't political."
The BLM movement has poisoned hearts and minds. It has taken the focus off the real problem for heavily minority communities - crime - and made that problem worse by endangering and alienating the cops they need most to help them.
Now Barack Obama is saying "we need to stop all the racially divisive language." As not only the president, but a president who thrives on identity politics, he has been the single loudest mouthpiece for racially divisive language!
Granted, I don't think it is typically fair to paint an entire movement based upon the actions of a few disturbed individuals - but BLM is a fraud. When you sow lies and phony victims, the movement has culpability.