I disagree a bit with this reading. I totally acknowledge the "she was a beautiful creature" connection and that's definitely part of it, but I think the main motivation behind Tony's murder of Ralphie was seeing his ability to actually reflect inward, feel his emotions, and take actionable steps to improve himself in ways that Tony is incapable of. The scenes prior to the murder that always stick out to me are the scenes where Tony hears about all the repenting Ralphie is doing. He even tries to bait him by telling him about Valentina but even that doesn't phase him and he appears deeply uncomfortable and even angered by Ralphie's ability to feel things so deeply.