Why do you think john molested dean?
I don't actually think it's canon. There is just a lot in the show that supports this interpretation for creative writing. Everything I write about johndean and wincest comes with small text that this is all fan interpretation and I'm not a delusional person who thinks it is canon.
Now we have established that I am media literate, I'll break down some of the context in the show that supports my interpretation. And by support, I don't mean proves, I mean it's what compels my creative interpretation.
John consistently transfered adult responsibilities onto Dean from a young age. Let's break this down.
Instrumental caregiving: Dean was made partially responsible for Sam's care from a young age. No, he didn't raise him alone and yes, John was still a father, but he left Sam alone with Dean from a young age and forced Dean to be his co-caregiver. Dean was denied a normal childhood in many ways, including being made to be a caregiver way too young.
Emotional parentification: John received emotional support from Dean from a very young age because Dean was exposed to John's difficulties. John talks about this to Dean before he dies (quote about Dean hugging John and telling him it's okay after a hunt) and it's also in his journal, although this is technically a noncanonical publication. He relied on Dean for companionship too: Dean was someone he could talk to about hunting etc.
Role reversal: John treated Dean more like a co-parent and partner than a child. Dean was less John's son and more whatever he needed him to be to support him.
Convert/emotional incest between John and Dean.
Trauma exposure and trauma bonding: John shared traumatic information with Dean from a very young age: how Mary died, that monsters are real, that John hunts them, his pursuit of revenge through what is technically murder, and the fact he devotes his life to violence and killing. Sam was protected from the truth for a lot longer, meanwhile John and Dean shared this trauma which bonded them closer. This is part of the reason why Dean is so defensive of John compared to Sam.
John created an 'us against the world' family structure, teaching Dean that everyone else is a danger and he can only trust John (and Sam). This isolation created enmeshment and codependency. It's also a tactic used often in grooming.
John blurred the boundaries between parent/child and adult/partner roles.
John treated Dean as an emotional confidant and relied on him for emotional regulation.
Child endangerment: John put Dean in life-threatening situations from a young age, including using him as bait which is especially disturbing given Dean described it as 'the wide-eyed hitchhiker routine', suggesting Dean was exploited by being placed into the role of a sexualised lure, using his looks to attract attention.
Neglect: John left Dean and Sam alone for periods of time. They were deprived of safety, support, and care. Neglected children often become desperate for parental attention and would do anything for it, which is easily exploitable.
Identity issues: John taught Dean his value/purpose is solely within his own mission. Dean did not exist as an individual but as an extension of John.
Militarisation: John literally made Dean into a child soldier. This further compounds the exploitable power imbalance between them.
Devotion and loyalty: Dean is completely devoted to John in the early seasons. It's often highlighted how he never turns down an order, always does exactly what John wants, always takes his side, and never questions him. When Sam points this out Dean says 'it's called being a good son'. The expectations of total obedience on Dean are far more extreme than in a normal parent/child relationship.
Loneliness: Dean is an extremely lonely person. He struggles to form bonds with other people because of how he was raised, with his strongest bonds being with family (John, Sam, and Bobby who though not blood related is undoubtedly family). In fact, when he does connect with other people he automatically assigns them familial roles because only family can be trusted, so Castiel and Benny are like brothers to him.
Hero worship: Dean does not have a normal or healthy view of John in early seasons. Later he starts processing his trauma and acknowledges that John was 'an obsessed bastard' and Dean didn't deserve what John put him through, but it's established early that Dean literally worshipped John. He says so himself.
All this does not guarantee sexual incest developing, but it sure as hell lays the groundwork for it. Their relationship is extremely fucked up, codependent, and unhealthy. Dean is deeply traumatised. These transgressed boundaries and blurred roles could cause a lot of psychosexual issues and crossed wires.
Dean is very CSA survivor coded to me, a CSA survivor. He struggles with intimate relationships beyond hookups. He fears being vulnerable and emotional intimacy. He has a strong fear of abandonment that often shows up in his relationship with Sam. He became as independent as possible to avoid needing other people. He could be interpreted as hypersexual, using sex for validation, self-soothing, to bolster his self-worth, and to be in control. He specifically seeks out potentially risky and emotionally detached sex. He has incredibly low self-worth. He self-medicates with alcohol to numb himself (granted, for many reasons). He feels like damaged goods. He is shown binge eating sometimes and food issues are common. He is often uncomfortable being touched by anyone except Sam (who is safe to him). He has an intense need for control.
He constantly makes jokes about being treated sexually. He uses his looks to his advantage but is also uncomfortable when people comment on them (gwen saying he has delicate features for a hunter, etc). The whole being used as bait thing is honestly horrific.
There's the comment from Hendrickson about 'your daddy no doubt touched you in a bad place'. Dean being described as 'daddy's blunt little instrument'. Other comments I can't recall off the dome but you get the idea.
If it isn't yet obvious, I write johndean as a way of processing my own trauma, and also as a way of making it worse, if I'm being quite honest. I have experienced most of what I outlined above (parentification, emotional incest, trauma bonding, enmeshment, isolation, neglect, abuse, etc) on top of CSA and incest. Why do I write this stuff? God knows. Is it healthy? Probably not. Why do soliders write about the war when they come home? Why does art often come from a place of deep emotional pain? It's just a way of getting what is inside out, and for me, johndean functions as my paint and my typewriter ink.
Also: it's just fiction. Some people like writing/reading dark fiction. That's cool too. Some people like fluffy romance where everything is healthy and sunshine and rainbows, some people like pain, trauma, and angst. People can like what they like. The people who enjoy reading or creating johndean content are no less valid for their interest if it's just something they vibe with and not a trauma response. Some people just think it would be hot if the ultimate dilf fucked his pretty son. Let people get their freak on.