I actually thought Shapiro’s answer was very good. It is a classic liberal idea (Jewish too) that people are not destined to be good or evil but are the products of the environment and their choices. So why kill the baby Hitler when having him be adopted by a loving family in Canada will also prevent the Holocaust?
And if your answer is “well that is not an option in the hypothetical,” then the response should be that your hypothetical has no application to the real world and is therefore a wast of my time.