Someone pulled that one on me once when I was ushering. Not only was “Can I help you?” technically correct, because he was staring at his ticket, so I was asking whether I could alleviate his situation (finding his seat). I instead just smiled. I wanted to say, “You know, not only was I technically correct, but English is an evolving language, and ‘can I’ has entered into the vernacular.” Nonetheless, I have endeavored to say “May I help you?” as it is more polite to ask permission to be of assistance. I actually usually did; but it sometimes came out the other way. In any event, his snotty reply to someone trying to help was far ruder than anything I did.
Looks as if that already happened (or maybe they’re just crumbs)