Dean knew John had tried to be a good dad. He'd loved his boys, done what he thought was right, prepared them for a world most people should never even know existed, let alone little boys that meant the world to him, little boys he wanted prepared for that world.
That didn't mean John would have won Father of the Year. Sure, Dean loved his dad, and Dean believed his dad had done his best in most of the situations he'd been thrown into, but the older Dean got, the more he realized that some of the things John had done and said weren't what people would call accepting or open-minded.
Dean swore to himself as a teenager that if he ever had kids, he'd love them no matter what, accept them no matter what. He'd let them be whoever they wanted to be. Dean knew his dad loved him, would kill and die for him, but the acceptance of whoever Dean wanted to be, well, that was an area where Dean was pretty sure his dad fell short.
It wasn't until he was in his twenties, though, that Dean fully understood what he'd let his father and society do to him. Living the way they had, Dean wasn't exposed to a wide variety of people for more than a short period of time when he was helping them, and when someone was scared for their lives or being attacked by something supernatural, it wasn't the best time to sit down and discuss feelings and other shit like that.
So Dean had stuffed his feelings down. He had built a wall. He'd developed a persona for himself. It worked well enough. He was attracted to girls his whole life anyway, so it was easy enough to fake the other shit.
When it came to hanging out with guys at school, he'd quickly learned to act like the loner. Not only did girls get a kick out of that, but he didn't have to put up with teenage boys.
Dean never fit in with boys. He felt disconnected. He never thought the way boys did. It was painfully obvious to him from a young age. It wasn't that he played with dolls or dressed up in pink outfits, danced about saying he was a pretty, pretty princess. No, Dean just knew his brain didn't work the way other boys' brains did.
Right about the time girls were saying boys were stupid and gross, Dean began agreeing with them. Not that he never did gross things himself, he wasn't a big baby, but boys just had this way about them that grated on him when girls never grated.