.. Most women would appreciate being seen as people who are capable of making their own decisions without someone else's unwanted input, Derek.

I'm saying this as a friend, Derek, but I'm going to be brutally honest with you. You're not looking out for her. Stalking her on a date is not looking out for her. It shows you don't trust her, or her boyfriend, to make decisions for themselves.

[He's trying to be delicate about this, Derek, but really, now...]

Also, you did not 'let' her date that kind because she never needed your permission in the first place. That's not your decision to make. And if that's how you behave with all the women in your life, then it's no wonder so many of them do not want anything to do with you.