This is rather unfortunate!
A man that looked like Santa Clause was visiting WDW yesterday (didn't say which park). A group of kids suddenly thought he was Santa and started to gravitate around him. I suppose he played along with that, but that got him into trouble because he isn't one of the "approved" characters. This resulted him being booted off the park!
I guess Disney did not want the guests to think that this person was one of their characters and cannot control or monitor his behavior (heave forbid that this person might start molesting people). Still, its is unfortunate that due to how he looks, and through no fault of himself, he was unable to stay at the park.