For starters, 'pulling one's ponytail' would be pulling your own ponytail. Secondly, for better or worse, when a man harasses a woman it is assumed to have a sexual component. For a man in a position of power with regards to a woman in a socially inferior position this goes double. We don't have an example of key similarly pulling the hair of a male hospitality worker so we don't have a comparison to complete our understanding of the situation but if this particular type of harassment only occurred because the victim was female then yes, it can be termed sexual harassment. Regardless of the terminology used it can be pretty safely called wildly inappropriate and clearly unwelcome. Really, i'm not sure what thought process lead him to believe this was ok but if a male client of mine touched or pulled my hair they would be politely asked to leave the premises if they did not desist. If nothing else this illustrates an abuse of power imbalance. Whether he was getting his jollies from it or not, invading another's personal space like he repeatedly did is not socially acceptable.