It might seem like a small thing, but I think it matters to point out that some people are awfully fond of using initialisms and abbreviations because it obscures the actual name of the group to which they're referring.
"BLM are terrorists" sounds a lot more legitimate than "Black Lives Matter are terrorists."
"Antifa are terrorists" sounds a lot more legitimate than "antifascists are terrorists."
So if you're arguing with the people who say this stuff (and I'd honestly recommend against doing so), maybe rephrase their statement to give the full name of the group to which they're referring. "Let me get this straight-- you're saying people who say that black lives matter are terrorists?" Or "Let me get this straight-- you're saying that antifascists are terrorists?"
Of course it's possible to adopt a nice-sounding name while your actual activities do not live up to that name-- look at the Liberty Caucus-- but it's quite another thing to say that hundreds of thousands of people across the world who claim to be supporting racial justice and opposing fascists actually fall into that category.