This is something I've being doing both a lot in real life and online. Whenever an NPC brings up BLM, switch the conversation to the 2016 Dallas shootings where a BLM protestor killed multiple cops. Say that it proves BLM has always been violent.

They have a really hard time dealing with this fact. Most of them conventiently forgot it. Bonus points if you mention how BLM disappeared for 4 years until the 2020 election.