In a post to the popular Reddit forum r/AmITheA**hole, u/7675465676—also known as the original poster or OP—asked the AITA community if she was in the wrong in her post, “AITA for arguing with my daughter’s dad after he told her about his diagnosis?” She earned over 5,700 upvotes and 2,500 comments for her trouble.

She says she divorced her husband three years ago. Though they used to share custody of their 13-year-old daughter, “Leah,” since the diagnosis, Leah’s been staying with her mother. She hadn’t been to stay with her dad in two weeks, so her dad and aunt came over to visit.

When they got there, he asked if he could have a private moment with Leah. OP agreed, but after she heard a “commotion” in Leah’s room, she came in to see what was going on. She saw Leah hugging her dad and they were both crying. OP was upset, and asked why Leah was crying, but she wouldn’t answer and left the room. Left alone with her ex-husband, OP asked what happened, and he revealed he’d told Leah about his cancer.

“I was in shock I asked if he seriously did that and he looked at me confused. I told him he shouldn’t have done that without telling me,” she wrote. “He looked even more confused and said that Leah needed to know because he needs her as part of his support to recover and said that he didn’t get how and why he was supposed to wait for or consult me.”

The OP objected, saying that him telling Leah without sharing his plans with her mother was unacceptable. He countered by saying that Leah’s his daughter too, and he didn’t need her permission.

“I told him he made a huge huge mistake because of how this can (and will) effect her mental and emotional health. he responded by saying that I was unreasonable to expect him to hide his diagnosis from her and act like he’s okay when he’s not,” she wrote. “he called me selfish because I know how his health will impact his time with her and he doesn’t want her to think he’s neglecting her when he’s going through rough times.”

OP, however, said that Leah wouldn’t notice because she was living with her now during treatment. Leah’s dad tried to leave, she said, but OP tried to block him, saying that they weren’t done. At that point, his sister came in and joined the fray, arguing and telling him to get ready to leave.

“She chewed me off for about 5 mins about how I should stop having expectations of her brother and acting like I have authority or legal connection to him then I had her leave cause I couldn’t take it anymore,” OP wrote. “We haven’t talked since then because his sister has been all over me about it.”

It’s very difficult to tell a child that a parent has cancer, but according to the American Cancer Society (ACS), Leah’s dad did it right—or at least tried to. Though the organization points out that children of different ages require the message to be tailored differently, the general plan ACS lays out remains the same.

The first step is to talk to the child alone, in a quiet space where there will be no disruption. That way, the ACS says, the child may be more willing to ask questions. The Society also says that since it’s often painful for a child to open up and be vulnerable, a disruption may derail this opening up and the child may not choose to again.

It’s also important to remain calm, and try to lay out exactly what’s going on. Children should be told the cancer’s name, location and treatment plan, as well as how their own lives will change during the treatment. Of course, the amount of detail depends on the age of the child—the ACS says a young child wouldn’t understand information that’s too detailed, though a teen will likely want to know as much as possible.

Finally, depending on the age of the child, the ACS says it’s important to make sure that the child knows that cancer isn’t contagious and that the cancer isn’t anyone’s fault, let alone their own. Though “magical thinking” is more common in younger children, the ACS adds that teens can often feel guilt about a parent’s cancer diagnosis as well.

Redditors were gobsmacked by the OP’s argument with Leah’s father.

“I can’t believe you really have to ask. [You’re the A**hole],” u/raq wrote in the top-rated comment with over 9,700 upvotes.

“If OP is really worried about her daughter’s mental and emotional health schedule a few sessions with a counselor so she can talk it out with a neutral person. Not wanting to tell your daughter makes [you the A**hole],” u/Many_Swimming_1529 added.

“As someone who had a parent go through cancer with a 50-50 chance of survival when I was in my mid teens; op’s daughter absolutely deserve to know and needs to know. Yes, it will affect her. Yes, it might affect her grades. But guess what? Not telling her, not allowing her the knowledge, chance and the time to process and handle it? That’s some utter bs right there. I thought this was about op wanting to be part of telling the daughter. But no. Absolute [You’re the A**hole] for wanting to hide this,” u/Majestic-Seesaw9362 wrote.

“My ex husband was diagnosed with cancer when our son was 5. It would never have occurred to me to hide it from him… and he was FIVE,” u/HappyGiraffe wrote.

“The fact that you’re asking in the first place… [You’re the Ahole],” u/FiftyJumps wrote. “You made one of the toughest moments of someone who has cancer about you… [You’re the Ahole]

“You didn’t offer comfort or encourage either of them… [You’re the Ahole],” they continued. “There’s so many but that’s a few… Oh and one more… [You’re the Ahole]”

Newsweek reached out to u/7675465676 for comment.