The level of bluntness one would need to get through to the typical blowhard described here is higher than many people are comfortable exercising except as a last-resort, bridges-burning nuclear option.
Certainly in the UK we'd tolerate all sorts of social torture before dreaming of "causing a fuss", although I appreciate OP is in the US!
To me this is just so sad. With a bit of empathy you can actually tell them that you are busy or not in the mood. It only gets awkward because or if you try saying it without saying it, if you show them you feel uncomfortable (in what could be a completely natural interaction between people in the same group who spend a significant amount of time around each other). The other person probably feels a bit lonely if they try to find somebody to talk to repeatedly. Of course, the direct approach works best if there actually is empathy, in the story here the only feeling shown for the other person is a pretty negative one.
I’m a non-claravoyant person and now a US->UK immigrant to boot. I often wonder how many people secretly hate me for doing something I’d be happy to change. Sigh...
Certainly in the UK we'd tolerate all sorts of social torture before dreaming of "causing a fuss", although I appreciate OP is in the US!