@whatzaname @theogrin @migriverat @lillyfinch @JuliusGoat
Let's Assume It's True is a good technique. Assume the claim is true, then follow its logic until it disproves itself. Beau of the 5th Column on YouTube is great at this.
Space. Control the space. If additional people are commenting, it's ok to ask them to refrain to keep a calmer, less confrontational conversation. (You may want to ask them through private message, at your discretion.)
Also, you can pause the conversation. 3\x