What "I love you" really means from mom and dad

I came across an interesting article entitled When a Parent’s ‘I Love You’ Means ‘Do as I Say’. This article described a parenting disciplinary tactic called "conditional parenting."  In this tactic, parents show love and affection to their children only when they are good and only when they earn it.  As a form of punishment, they withhold affection.  This type of parenting is advised by parenting figures like Dr. Phil and Supernanny, and it is a tactic that is shown to be somewhat affective.  Generally, children who are disciplined in this way act like they're parents want them to.  However, these children tend to be more resentful of their parents and also feel more pressure from their parents.  This article quotes "Supernanny's" parenting book which says: “the best rewards are attention, praise and love,” and these should be held back “when the child behaves badly until she says she is sorry,” at which point the love is turned back on."  The love between a parent has for a child is supposed to be unconditional, is it right for parents to use love and affection as a tool to get their child to act a certain way?