Not true. The message being sent is that all whites have benefitted from the systems of racism, while minorities have suffered. That's a very different message than, "You are a racist." and it's also unfortunately sad that so many of us can't admit to being fortunate to be given opportunities that others haven't because of their skin color.
A second message being sent is that being silent, being unconcerned, being in disagreement with the notion that whites have benefitted while minorities have suffered is to choose the side of oppression. That's a different conversation, but it's still hardly something that should be taken as a personal attack. It's a plea to listen and to see, to have compassion and empathy, to look out for each other.
So when some of the people leading a BLM protest chant "What do we want? Dead Cops! When do we want them? Now!" and "Pigs in a blanket, Fry em like bacon!" They're just good, concerned citizens letting people know that we lack compassion and empathy.
Please note, I used the word some,not all. It's probably best when talking about these issues not to lump everyone together.
BLM is very decentralized in the sense that any person or people can claim it while doing things not represented by the 'official' movement. As an actual organization, BLM hasn't and wouldn't ever spout rhetoric like this, and is consistently quick to condemn rogue people trying to hijack the movement for obviously hateful and misguided agendas.
^