Author has written 1 story for Harry Potter.
I dislike slash for the same reason I dislike a lot of other fanfiction.
Yes, fanfic is there so that you can make your own changes to canon, whether those changes take the form of simple addition or continuation... or, actual alterations of the universe.
If you make a significant change to a character's background or behavior, or likewise alter the workings of the established universe, you must give convincing, satisfying reasons for doing so. You have to take the time, in story, to explain these changes.
If you fail to do this, the only readers that won't complain are those too lazy to write a review, and the ones that are too vapid to notice, too apathetic/complacent to be bothered by it, or so eager for the intellectual equivalent of reheated fast food you're serving up to ever dream of being offended at the notion of being fed blatant garbage and empty calories.
Harry is straight in canon. I don't care what kind of a numbnuts conspiracy monkey you are, you cannot argue that. JKR would have been more than happy to out him in an interview, were he actually a gay man resigned to marrying a woman just for the acceptance of his ersatz family.
Bearing this in mind, any imagined subtext of Harry's supposed homosexual leanings are just that, imagined. However, yes, you could try to stretch any would-be sub-textual clues into actual facts in fanfiction.
The problems flood in when you see that the vast and overwhelming majority of slash writers don't want to do the legwork necessary to realistically turn straight, canon Harry into gay Harry. They want instant satisfaction of their masturbatory and/or wish-fulfillment fantasies, not a hard slog through the landscape of writing a realistic story about an abused and neglected boy, who has the weight of the world on his shoulders and the eyes of a fickle populace scrutinizing his every move, discovering his own sexuality and his struggle to reconcile that with his loveless upbringing and the possibility that his homosexuality could make him even more hated than he already is -to say nothing of what his homosexuality could mean for the future of his family name, as the last Potter in a society that often values blood and tradition above all else.
This lack of effort to make the story BELIEVABLE is compounded by their incessant need to pair Harry with either scumbags whom he wouldn't touch with a ten-foot pole, or with old men he has even less acquaintance with than interest. Seriously, Draco? Lucius, Snape, Remus, Sirius... VOLDEMORT!!!
What the abstract fuck?
This drooling, panting need to put leather pants on the villains is often the first and biggest rotting brick in the shoddy so-called foundation of nearly every slash fic ever.
And what attempt is made at explaining Harry's sudden and complete 180 in sexual preference AND his sudden attraction to people he wishes didn't exist and/or said people's miraculous transformation into good guys who no longer look like pale, scrawny rats; albino snake men, or greasy, hook-nosed troglodytes, with filthy oral hygiene?
None. The majority of the time, there is no explanation, justification, or even a "Tell, Don't Show" heads-up to let you know this is a complete AU where the villains are all bishonen, gay hobos frolic on Big Rock Candy Mountain, and -oh, by the way- Harry is a shirt-lifter who loves to bottom for the people who have collectively been ninety-seven percent responsible for making his entire existence a living hell.
And, yeah, why is Harry nearly always the bottom? Not just 'on the bottom' but an actual, 24/7 submissive. It can't be because he's "so pretty", since that's supposedly Draco's stock in (the rough) trade as well, yet he's still the one usually bending Harry over.
Although, considering the dubious efforts made at pairing him with a 'good guy' usually lead to him bottoming for Cedric Diggory during Harry's fifth year... Yes, Cedric, whose death is completely ignored, rather than the author even making the negligible effort to retcon it in an author's note. He's alive; don't question it. These people can't think the hard thoughts, because it would require them to remove at least one of their hands from their privates, or their page down key, and they can only do so much at once.
Of course, some pair Harry with Cedric during the Tournament... so you have the squick of socially-isolated, young, inexperienced, Harry being 'groomed' by a prefect, legal adult, and competitor in a potentially fatal contest.
No conflicts there.
Of course, I think Harry/Cedric is mainly just a way for the Twilight 'schlick-girls' to pair Harry and Edward Cullen without having to bother writing an actual crossover.
And the reasons for Harry/Cedric are every bit as valid as those for Bella/Edward.
Which is to say that, at best, there are no reasons and, at worst, it's equal parts lame and fucking creepy on every goddamned level.
So, yeah, Harry/good-guy isn't so great, either.
Most slash is just as fail-tastic as the fics that start out with Harry discovering his parents left behind a hidden bachelor pad with a widescreen plasma TV, Blu-Ray player, and a full complement of modern game consoles... even though they died decades before those things existed, just because the writer really wishes they had a mountain of free, hi-tech swag suddenly dropped on their doorstep.
Except that the slash is worse, for all the reasons listed above.
Not my words, but I agree with everything said.