It was a different time, I guess they didn't see it for what it was.
Back then, girls were socialized to be nice and agreeable. The adults thought it was cute and funny that this creepy boy "liked me so much." I think we know better now and hope we do better by our girls.
As for my change from nice to not nice, it's a bit of both. I no longer feel the need to placate others or the pressure to give the time of day to those I want nothing to do with. And "fuck off" works pretty well as far as a language change, LOL.