After seeing the differences in how Rumple trained Cora and Regina in magic and how Gold coaches Emma, I find myself going back to his fascination with bottling True Love. While intellectually he might have known (and probably did) about the reputed power of True Love, I don’t think he was especially interested in it until Belle. He mocks it even on the day he takes her home with him. But after having experienced its power for the first time himself, he gets on the Snowing wagon quickly–in part for the power of it, but I think he’s actually sincere when he tells people at that point that he’s a fan of True Love (as well as what it creates).
So perhaps, having been exposed to that power, he’s realized that anger and hatred aren’t the only ways to invoke magic. I think there’s reason to believe that he couldn’t comprehend that until he fell in love with Belle.
Keeper of Belle's Gold magic, sand dollar, cloaks, purple FTL outfit, spell scroll, library key, copy of Romeo and Juliet, and cry-muffling pillow, Rumple's doll, overcoat, and strength, and The Timeline. My spreadsheet: https://drive.google.com/file/d/0B6r8CySCCWd9R0RUNm4xR3RhMEU/view?usp=sharing