How do you react when someone asks you to describe something, then responds to everything you explain with disinterest or derision?
You punch them in the throat, of course. Then run away laughing.
Unfortunately, you can't punch people through the internet. Yet.
A friend asked me to describe what happened over the weekend, and responded to everything I said with something along the lines of "I don't care. Keep explaining though".
I have this exact friend. It's super frustrating. In his case though, he thinks being disdainful is somehow funny, as though I'm somehow part of the joke he secretly decided to start acting on. I've found the best way to deal with it is call them out on their bullshit. Something along the lines of "You know, why I do I even bother to talk to you? You can be such an asshole it ends up being a waste of my time." ACTUAL friends will respond to that. People you need to punch in the face will reply with more disdainful bullshit, or try to play it back on you.
Honestly ask yourself if you care about this person, and ride out the emotion dealing with their nonsense generates in you. People like that get used to a circle of friends who put up with their idiosyncratic bullshit. Letting them know you're not person will either a) end the relationship or b) cause them to reevaluate how they talk to you. I've gotten better at reading my friend's moods, so I better understand when a "joke" is on the horizon. Likewise, he's learned about me that after I certain point, he stops being enjoyable to hang around and I have no problem walking away when his ego masturbation gets on my nerves. These people need an audience for their schtick to work, so deprive them of one.
In the end, they're posturing at you because they think they're successfully projecting the way they want to be seen. Deflate that shit.