Is it abuse to tell kids that they have great value regardless of what others say?
Teaching children about Hell is common assault, because it causes a credible fear of injury. Children don't have the capability to distinguish between imaginary threats and credible ones, especially when the threats come from their primary caretakers.
Using threats of Hell to obtain obedience is extortion.
Teaching children about Heaven in order to obtain obedience from them is fraud.
Most Christians also hit their children, which is battery or aggravated assault, depending on the circumstances.