http://www.fanfiction.net/s/5782108/6/Harry_Potter_and_the_Methods_of_Rationality said:
McGonagall pointed toward a store that looked as if it had been made from flesh instead of bricks and covered in fur instead of paint. "Small pets are permitted at Hogwarts - you could get an owl to send letters, for example -"
"Can I pay a Knut or something and rent an owl when I need to send mail?"
"Yes," said McGonagall.
"Then I think emphatically no."
McGonagall nodded, as though ticking off a point. "Might I ask why not?"
"I had a pet rock once. It died."
"You don't think you could take care of a pet?"
"I could," Harry said, "but I would end up obsessing all day long about whether I'd remembered to feed it that day or if it was slowly starving in its cage, wondering where its master was and why there wasn't any food."
"That poor owl," McGonagall said in a soft voice. "Abandoned like that. I wonder what it would do."
"Well, it'd get really hungry and start trying to claw its way out of the cage or the box or whatever, though it probably wouldn't have much luck with that -" Harry stopped short.
McGonagall went on, still in that soft voice. "And what would happen to it afterward?"
"Excuse me," Harry said, and he took McGonagall by the hand, gently but firmly, and steered her into yet another byway; after ducking so many well-wishers the process had become almost unnoticeably routine. "Please cast that Quietus thingy."
"Quietus."
Harry's voice was shaking. "That owl does not represent me, my parents never locked me in a closet and left me to starve, I do not have abandonment fears and I don't like the trend of your thoughts, Professor McGonagall!"
The witch looked down at him. "And what thoughts would those be, Mr. Potter?"
"You think I was," Harry was having trouble saying it, "I was abused?"
"Were you?"
"No!" Harry shouted. "No, I never was! Do you think I'm stupid? I know about the concept of child abuse, I know about inappropriate touching and all of that and if anything like that happened I would call the police! And report it to the school principal! And look up government offices in the phone book! And tell Grandma and Grandpa and Mrs. Figg! But my parents never did anything like that, never ever ever! How dare you suggest such a thing!"
McGonagall gazed at him steadily. "It is my duty as Deputy Headmistress to investigate possible signs of abuse in the children under my care."
Harry's anger was spiraling out of control into pure, black fury. "Don't you ever dare breathe a word of these, these insinuations to anyone else! No one, do you hear me, McGonagall? An accusation like that can ruin people and destroy families even when the parents are completely innocent! I've read about it in the newspapers!" Harry's voice was climbing to a high-pitched scream. "The system doesn't know how to stop, it doesn't believe the parents or the children when they say nothing happened! Don't you dare threaten my family with that! I won't let you destroy my home!"