There is a really good reason why teens are mean to their parents. Now with this new teenage brain growing by leaps and bounds, they are literally having thoughts they have never had before. Remember back when you were a teenager the moment when you realized " hey, my parents aren't perfect...awesome!!!!"
Teens have this new thinking ability that allows them to analyze and think more deeply about things. This is why teachers in middle school and high school expect their students to go from the concrete: who-what- where kinds of questions and answers, to the whys? They want them to read between the lines. School is not the only place teens are expected to do this kind of thinking. Their social life, their family life, all of it is now seen and understood under a whole new lens. What do you think gossip is?? It's a new way to think and analyze the people in their life. And you dear parents are part of their life. For the first time, they are seeing you without the rose-colored glasses of childhood, where parents are perfect, and their #1's. Now they see cracks in the armor. "Hey my parents don't practice what they preach, they can be hypocrites." Your teen can see right through the "do as I say, not as I do!"
Not only do they see you more realistically, but they absolutely love to tell you all their new perceptions that they are having about you. They are missing the edit button that will come with adulthood. For now though, if they have a thought about you, no matter how mean sounding, they share it. You may feel that no matter what you do or say, according to your teen it's the wrong thing!!!!
Never fear, this is only temporary. Remember it's a new way of thinking about you. It's a novelty, and it feels really powerful for a teen to be able to see their parents in a whole new way. Having a teen in your home is like having a live in therapist. There is no one who will be more honest with you. If you can hold off on getting defensive, and listen to what they have to say, you might learn something new about yourself that is useful.
The trick here is to not feed into your teen's feeling of power. Basically they are being bullies, and the best way to handle a bully is to take away their power of hurt. So the next time you feel that biting criticism from your teen, rather than expressing hurt or anger, go up to them, give them a great big hug and say: "You are so cute when you're being a brat, I love you!!!" That ought to do the trick!