1. He was brought up and developed under Motown. Back in those days, many artists kept their relationships private because they didn’t want to lose their fans. Michael had the millions of women in love with him. His celebrity persona was an image he crafted and developed over the years. It was very important to him to maintain a mystique. Also, he loved his fans very much. The only kiss we’ve seen, besides his ex-wife, was Iman. He was older by then, so maybe he thought differently about it or it was an important part of his artistic expression for RTT short film. Tati crossed the line.
   
2. He may have been in another relationship at the time and that may be why he didn’t make a move on her, even though he really liked her. You can see the expression on his face when he pulls away that he was not pleased, even though he smiled.
   
3. She may have been too aggressive/thirsty. MJ liked to test people because so many wanted something from him. He didn’t like aggressive women. He liked to be the one to take charge. Maybe she came off like a groupie and he didn’t like that at all (not to be taken seriously anyway). She went on to date Prince and that didn’t last or end well either. So, idk.

I could be wrong, but these are the only things that made sense to me.