Oh dear. The hentai that everybody loves to hate. "A hentai for the Catholic priest who wants a fap before bedtime." Yes.
In all honesty, I think, after hearing everyone's anecdotes about how it scarred them for life, I was expecting a lot worse. I was seriously expecting to feel incredibly uncomfortable, since pedophilia is one of the few things in this world that actually gets to me. I put off watching it for quite some time because of this fact. But when my morbid curiosity finally got the best of me, it didn't make me that uncomfortable. The good thing about hentai is that it helps people indulge in their fetishes in a way that doesn't actually harm any real people. Like, it's guaranteed that you aren't watching somebody ACTUALLY being exploited and/or raped on camera, and although the fact that it's unclear how old Pico actually is (he could probably pass for between 10 and 14 in my opinion but who knows) did make me uncomfortable, it could have been far, far worse. For example, he could have been straight up, no grey area, against his will raped, or really, really obviously 8 years old or younger even. But he wasn't. I guess something good to say about all the fucked up hentai in this world is that at least people most people who are watching that hentai are watching hentai instead of idk decapitating people or raping children for sexual pleasure.
What made me cringe and want to cover my eyes was a) moving genitals and b) the sound effects... oh god. The SOUND EFFECTS, my friend. Horrifying. But, I seriously think that if you took the element of homosexuality out of this hentai, nobody would bat an eyelash. It'd be just another loli hentai and nobody would care.
I think part of what it is about this hentai that makes people want to gouge out their eyes is the fact that it puts them in an uncomfortable position - as someone who has no real preferences when it comes to the gender of a sexual partner, I fully see why people hate Boku no Pico so much. Don't take my word for it here, but I'd estimate that the majority of people who watch porn they know will make them cringe and/or laugh are probably straight males. So (unless you're into futanari) when you watch a hentai in which a male character could totally pass for female having yaoi sex and making feminine-sounding sexual noises you might hate yourself for getting a boner or, at the very least symptoms of arousal. That's my theory anyway.
In the end, I suppose my opinion is that Boku no Pico wasn't as bad for me as it might be for others because it didn't make me question my sexuality, and I don't actually think it's shameful to have "weird" of "perverse" desires (being turned on by lolis or Pico included) because your desires aren't something you can control, and 'morality' isn't an objective truth, just a subjective system we put in place so that most of us don't get hurt.
As for the rating, how does one even rate hentai objectively? It's fucking hentai with no plot. This is probably how I'd rate just about any hentai.
Story: 1/10. I mean if you take away the factor of Pico's age, it's your average shitty hentai plot and they tried to throw in some drama at the end that went nowhere, idiotic.
Art: 5/10. No comment I guess, the art style was fine; it was what the art was showing that hurt me inside.
Sound: 1/10. The sound effects made me want to rip out my own ear drums.
Character: 2/10. It's a hentai, they're hentai characters.
Enjoyment: 2/10. I hated it but at least I wasn't bored.
Overall: 2/10.