Why I no longer believe in the "Don't Talk To Strangers" Rule

Posted this in r/TrueOffMyChest, but it kind of fits here too. I posted this before in r/AmItheAsshole. I mentioned this guy who gave my sister a ride home and she said she has lunch with him every few months. I tried to tell her that it's weird for grown man to befriend little girl. To give you an idea on how little she was, I was 7 and she was 5 when it first happened. I think he's 40ish. To make the long story short, I got roasted. (Yes I have talked to my parents, they are on his side. ) <br><br>Fast forward to few days ago, I got into an argument with this man. Mind you that I met him on one occasion. He was arguing with my dad about lunch/dinner plans. He was saying "I thought your daughter was going to go with me?" My dad replied with "What? No, she's going with me." He replied "Oh so you don't want me to hang out with her? Fine." This led to a huge argument. My sister started crying and saying that she wants to avoid conflict at all costs. My dad ended up taking her while leaving me with him. She doesn't even like him. She only likes him because he buys her food and lately because it matters to her that he was the one who gave her a ride home. She has said this before. <br><br>This is when I realized that this man is too touchy for someone who only met my sister on one occasion and she was 5. I have met him once, and I have always felt that he was too clingy and touchy. I'm a 9 year old. I think any normal human would recognize that something is off about him. But no. People are blinded by "Don't Talk To Strangers" rule. "He's a nice guy who has been friends with little girl for years." Yeah no shit. There's a reason why he matters so much to her. She was 5 when she first met him. She's now 9. What do you think he has been doing for the past 4 years?