by Samantha Connor He went there. Former HUD Secretary Julian Castro took a shot Thursday at Joe Biden, accusing the former VP of flip-flopping on health care -- and then basically suggested that Biden was senile, leaving the crowd shocked. “The difference between what I support and what you support, Vice President Biden, is that you require them to opt in, and I would not require them to opt in. They would automatically be enrolled, they wouldn’t have to buy in,” Castro said to Biden.“You do not have to buy in,” Biden responds.“Are you forgetting what you said two...