I hate to say it, but bruising your child, unless said child is one of those rare children who bruise when you look at them, is really over the top, in my opinion.
Especially if you look at this severe of punishment for wetting the bed, then what will he do if the child lies, or steals, etc.
On the other hand, if the state has the right to tell parents how to discipline, that opens another can of worms, given the politically correct, permissive, and paranoid leanings of the government. Then you have a spank equal child abuse.
Maybe it is just better to let a few extreme cases go for the greater good, since not disciplining at all is equally as abusive as over disciplining.