The BLM movement is controversial. It's not just about being anti racist, it's got political undertones. Describing those who defend it as 'anti racist' is topical. I don't really want to go into the history of slavery here as it's a bit off topic, but that poster held below is quite negative and aggressive. It doesn't look like a peaceful anti racist protest, it looks pretty inflammatory. He's not criticising anti racism, he's criticising BLM.
''But Mr Farage , former leader of the Brexit Party, described the scenes as “terrifying,” likening protesters to a “paramilitary-like force.”
“This is what the BLM movement wanted from the start and it will divide our society like never before,” he said on social media. ''
That's not really a 'slur'. He's not commenting on a group of black people walking peacefully and saying they're terrifying, he's commenting on scenes like the one below.