Since they are not told, in any reasonably accessible way, what is going to happen when they click "like", they have grounds to complain about anything that does.
That's not entirely true. I don't think "You ass anything you do is pubic" is a valid MichaelApproved quote. Now, i don't know how you could misrepresent a like, but i don't think substantial misrepresentation (like my ridiculously juvenile example) is allowed.
Right or wrong, that's the nature of these things.