The speaker is watching someone who hurt them deeply walk into their home and be treated like a welcome guest. The poem is built almost entirely from questions, and each one sounds less like a request for an answer than a cry of disbelief. "How can you stand there and smile?" the speaker asks, and then turns to the others in the room, who seem relaxed and happy to laugh along.
What stings most is the final question. The speaker is the one being scolded for not being polite, warm and welcoming, while the person they call a "monster" gets easy kindness. The poem doesn't say what happened, so we only know the harm was serious: it "ruined my life." The mood is raw, isolated and bitter. The plain, lowercase voice makes it feel like a thought the speaker can't say out loud. The title, "The World Makes No Fucking Sense," sums up the feeling of being unseen and unfairly judged.