I get what you mean about the fandom going crazy when it comes to John but he was not a good father. Dean canonically knew what it was like to be hungry for days, stole food for Sam, was "punished" (Dean was hurt by the way John acted afterwords and John never said anything like I forgive you) for taking breaks to be alone and calm down, and ignored his son crying saying he was at their old house and didn't know what to do and needed help. That isn't how a father should act, no matter what.
I agree. John fucked up a lot. He did a lot of bad things and Bobby was a much better dad to Sam and Dean. But John was a man who watched his Heaven selected, God approved soulmate burn to death above his six month olds crib. I think he was entitled to going a little crazy. You also have to remember that there is no canon evidence that he ever physically abuse Sam or Dean, I don’t think he ever would. Because he loved them. He was teaching them to hunt so that they would know how to protect themselves because he couldn’t stand to watch them die like the love of his life had. Also, Jeffrey Dean Morgan, who played John and knows him better than any of us, has said that he was a man that would do anything to save his sons, and in the end he did.