Is it wrong to kiss your kids on the lips? Doctor warns parents that it is 'sexual' and 'confusing'

Picture the scene: a mum drops her child off at the school gates, says goodbye and kisses her little one on the lips before departing.
How would you react to this? With disgust, concern or indifference?
And would you change your mind depending on the age of the child, or their gender?
An American doctor has sparked a fierce debate online after she suggested that parents shouldn't kiss their child on the lips at all because it could be 'confusing'.
Dr Charlotte Reznick, a child and educational psychologist at Californian university, UCLA, gave a quote to The Stir in 2010 when Harry Connick Jr was photographed kissing his eight-year-old daughter on the lips.

At the time, she said: "If you start kissing your kids on the lips, when do you stop? It gets very confusing.""As a child gets to 4 or 5 or 6 and their sexual awareness comes about (and some kids have an awareness earlier - as when we notice they start masturbating at 2 or 3 sometimes - they just discover their private parts and it feels good), the kiss on the lips can be stimulating to them."
She continues: "Even if that never occurs to a child, it's just too confusing! If mommy kisses daddy on the mouth and vice versa, what does that mean when I, a little girl or boy, kiss my parent on the mouth?

"If I had to answer when to stop kissing your kids on the lips, it would be now."

Her comments have recently gone viral again online, sparking yet another debate between parents - and among people who have no children.
Dr. Paul Hokemeyer, a family therapist, disagrees with the theory, telling Yahoo Parenting: "It’s important that parents keep and maintain boundaries with their children, certainly, but in terms of expressing affection this feels within the realm of normal."
What do you think?
At what age do you think it becomes unacceptable for parents to kiss their children on the lips, if ever?