I didn't think you personally took that picture, but your attitude of "it's perfectly legal" is rather off putting. Something being legal doesn't make it ethical.

Also, taking a pic at Disneyland with strangers in the background is different than taking a pic of a specific stranger for the purpose of humiliating them on the internet. You know this, I know this, most people know this. It cruel and wrong. Not that hard to parse out really.