Jesus, what is it with kids today. YTA. Stop dictating your father's life. Him getting into another relationship and remarrying isn't disrespectful to your mother's memory. To be frank, you don't bloody know what your mom would want. However, I think it's kind of clear she'd want your dad to live his life and not be miserable. I know it's probably hard for you still, but just because your dad moves on with his life doesn't mean that invalidates his relationship with your mom. Doesn't mean he doesn't still care about her.
You and this user are a match made in heaven: