I signed it too. I'm surprised anyone in the UK noticed or cared about what was happening here in the US, but apparently some of you guys do. Thanks for letting me know about it.
I've been fighting them for two years now. Lost a lot of friends, made a lot of new friends and enemies in the process. It hasn't been easy. A lot of people don't know what the movement really stands for, and they use a lot of rationalizations about White privilege or any means necessary being justified to stop Black deaths. But their data doesn't hold up to scrutiny.
If things continue this way, nothing good can come of it. BLM needs to be stopped. Their goal is essentially to create anarchy by overwhelming all the police forces. This has nothing to do with race if you examine them more closely. They're far-left anarchists, and little more. Black deaths are merely the justification for anarchy, not their real motive.
The thing about them is that you can't stick anything to them... they're like a hydra, one body with many heads. They can just disclaim responsibility if anyone tries to blame the organization as a whole, and claim it was just one faction that they can't be held accountable for. Which means you chop off one head, but can't kill the body. Everyone is expected to take them at their word rather than looking at what they do.