Define "demeaning". It is not a title of respect, but then, in Shakespeare's day, how much "respect" would a peasant expect from, for example, a nobleman? Read Shakespeare carefully, and you will notice that there is always a careful distinction between persons addressed as "thee" and persons addressed as "you". Is it disrespectful for a king to call a servant "thou", when the servant addresses the king as "you"? Thus, while referring to a girl as a "wench" might not show respect, it might also not be a show of particular disrespect, either.