Make me angry.

http://www.cherrypointyardsales.com/item.jsp?itemId=35900660&ref=mostRecent

Your dog is being dominate and marking?
Is he neutered? Had any type of training, ever? Crate trained? Taken out on a regular basis? Walked regularly? People are stupid. I've worked in rescue for over 10 years. Its really not that difficult to house train a dog or break bad habits. 

It sounds to me like there is honestly more to the story because they said it needs a home without children so I don't think it's just the marking. I think there are a lot of factors that added up and ones that they are not willing to share. A lot of people re-home dogs that have bit a child and then just point out other reasons they are re-homing and hide the fact that it is a biter and just request homes without children.