Wow! Nice discussion question!

I think that it is very possible for Tom Jr's anti-love being attributed to the fact that he was the offspring of a loveless relationship. However, I do not think that had Merope and Tom Sr gotten together without help of the love potion, that it would have made any difference in how Tom Jr turned out.

As I think it was Dumbledore who said this, though it might have been Hagrid, who was saying how some wizards just go bad. Regardless of how Tom Jr was conceived, it is still in his DNA to make him how he turned out. He was meant to turn 'bad'... to be on the dark side... to kill Harry. All of this was meant to happen, because if it wasn't then Trelawney never could have made the prophecy.