The irony of assumption
When we learn that Larry loves a girl named Juliet (a not-so-subtle allusion to Shakespeare), and we learn that his friend Johnny is already dating that girl, we are invited to fill in the rest of the story. "Oh, Larry is just a little insecure, so he's jealous of his friends who are in relationships." Ironically, that is not only wrong, it's incredibly assumptive and in this case, maybe even hateful. Larry isn't just randomly "a little insecure." He was raped for years by his own father, and he lives in a glass house of terror, never knowing what to do or what to say about it, and he's all but dying of loneliness. The author invites an ironic assumption, asking the reader to judge the character, but the implications are misleading.
The irony of Johnny and Juliet
In a way, it's kind of ironic that the secondary plot of the story is romantic (secondary because technically, the more important plot is Larry's eventual decision to confide in someone about his pain and trauma). Romance isn't exactly what the reader would expect a person in Larry's position to be thinking about, but that's exactly the point of this irony—Larry is not immune to normal human experiences, but he carries a burden that often prevents him from fulfilling those desires. He is desirous.
The irony of moving
Sometimes we talk about moving as though it were normal, but for a long time, moving was one of the most severe changes one could possibly endure. When one moves, the culture and social assumptions change around them, and they have to adapt to a new environment. For Larry, the move to Fort Rae was ironic, because it made him so incredibly isolated and lonely that it catalyzed him to make his first real friend, confiding in someone.
The irony of self-talk
By opening up to Johnny, Larry is forced to talk through his past, and if he had been ignoring it before, there's just no way to talk about something and ignore at the same time—he must be admitting it to himself too. Perhaps that is the real value of Larry and Johnny's friendship—by teaching Johnny about his trauma, Larry is forced to categorize it for what it is, and he is forced to be objective about the truth of his past. Ironically, the most important part of what Larry said to Johnny was actually whatever he managed to admit to himself in the meantime.
The irony of the event
When bad things happen, nature compels children to tell their parents. When a parent demonstrates that they might not be such a good person to talk to, children become confused and moody, because their parents (if they are good parents) are the only people the children can really connect with and talk with about problems. That's how nature was designed, not just for humans but for any animal that parents its young. So it's terrible and horrific and sad whenever an adult misuses their relationship to a child for evil, selfish purposes. Therefore the events that Larry tells Johnny about are ironic in the most tragic, painful way. Not only can Larry not trust his father with his problems, his father is the source of the problems, because he is a pedophile and a rapist.
