My experience is that people there think that none of the tourists visiting this island know their language, and say the most cruel things right in front of you. I have never experienced likewise. Just one example: Being at the market, stopping by a place looking for something to buy home for gifts for family/friends etc. (i had bought a drum from him a couple of days before, at the other market, Las Dalias) and the salesman started singing es una perra intruso... Loud. About me, just because i was there, looking a couple of minutes at the items he was selling... (Needless to say i didnt buy anything from him.) So, I smiled, said bye (in english, so i wouldnt embarass him) and went. When I actually wanted to say some few words back at him, but dont want to go on that low level. I had a couple other experiences too, but not as uncomfortable as this one... Be careful what you say in front of your customers, you might be talking the same language...
My impression is that people are not the nicest in Ibiza. Like you don't want customers.