Having been around or owned cats for 20 years I've seen this behavior many times. This cat is not happy about something. Some cats are naturally more jealous and need a specific amount of attention or don't like a recent change. If your taking care of your cat and keeping it's enviroment clean then your doing all you can. Otherwise your cat needs an attitude adjustment. Cat's are more like people in their fickleness and must be shown that they can't get away with this type of behavior. No there is nothing wrong with correcting your cat despite what others say just make sure you are patient with them before dishing out punishment.