Let me preface my comment by saying this.....THERE IS NO WAY THAT THE POLICE SHOULD HAVE BEEN CALLED TO EVEN BE INVOLVED IN THIS!!!! This was not a matter for the police, PERIOD!!!
With that said, once they WERE called, the officers' hands were tied. A property owner (or person with legitimate controlling interest, such as a business manager) has the right to ask any person to leave their property for ANY reason, even NO reason. If they ask you to leave, and you refuse, especially after the police show up and ask you to leave, it's trespassing. I don't think these cops wanted to make that arrest, but had no options.
Let me ask you this (crude example, but good nonetheless)......If a person showed up at your house with a friend, and you decide that you don't want them there. They tell you that they aren't leaving and plop down on your couch. No argument, no fight, but just plop down on your couch and refuse to leave your house. You call the police, and they show up and say, "Well they didn't do anything wrong, so there's nothing we can do", and leave without taking any action to get this person out of your house. You would be on the first thing smoking to file a complaint on the officer (after you whip the person on the couch's arse.....lol)
At the end of the day, this dumbassery is SQUARELY at the feet of the manager who called the police. The police are obligated to respond to a request for police service, and must follow the law in doing this. I don't see why Starbucks as a whole should suffer in this (unless there is something I don't know about where there is policy or standard procedure across their stores that they respond to this in this manner). This, to me, is more about the individual that happens to work for Starbucks, than Starbucks itself as a company. That said, I can't stand their coffee.....Too expensive, and way over the top.