I always saw this as a tragedy which Tom Riddle could not affect: it was the magic of love potion that made his father "love" his mother, but once the potion's strength ran out and Merope wanted to experience real love, Tom Riddle Sr. abandoned his "wife" and (unborn? I don't remember) child. To grow up without a father is not nice, but Merope couldn't handle it either and apparently her pregnancy was a hard one, since she died so soon. So young Tom Riddle was bereft of motherly and fatherly love due to no fault of his own, very similar to Harry Potter's eventual fate. But whereas Harry managed to remain relatively positive and nice young boy, Tom apparently became embittered and once he discovered his unusual talents, revelled in the power they offered to him. It was all about the choice to the end. Even with his dubious start Tom could have become something better (not necessarily greater, but much, much better). Instead he indulged his impulses and base desires. Whereas Harry could have become something much, much worse (no positive parent figure for the first decade of his life? Upon discovery of his talents becoming an immediate celebrity and being fawned by even the highest represantive of the wizarding government? He could have become a sociopath, quite frankly) and yet did not give in, save for the usual teenage angst and certain amount of selfishness. They had many similarities in the upbringing and even in personality, but they chose very differently.The Romulan Republic wrote:Merope might have done something rather horrible, but given the circumstances she grew up in and the way she died, I do feel sorry for her. Nobody deserves that. And if she hadn't been treated like subhuman shit her whole life, she might have turned out better.
Also, I hate the idea that being conceived by a love potion made Voldemort evil. Not only does it directly contradict the theme of people's choices being important by suggesting that Voldemort was made evil by his mother's actions, but it also implies that children conceived through rape are inherently bad people, which is a horrible message.
Tragedy shaped both of their lives, tragedy which neither could avert. But they had a choice, both of them. Tom chose to become Voldemort; Harry chose to be himself and to live as well as he could. Love potion was only an instrument in Voldemort's tragedy as was the death spell on Harry's.
However, love potion is ethically unsound. Either Rowling didn't think this one out (a strong possibility) or she wanted to say something about the wizarding world with it. In-universe, I'd say that the wizards are so used to the presence of various love potions that they really don't care anymore besides some obvious stupid jokes. And the Weasley Brothers aren't necessarily that responsible in any case - it was their love potion that made Ron a little bit.. strange, wasn't it?