fs, youre right. And something I always beleived in was to set the example. My boys are not allowed to let their room get too bad. They put their dishes in the sink. They help around the house....so even my 3 little boys set an example - one which this kid does not follow. So yup. I have some work to do here, I have to toughen myself up and start growling a bit :( but its annoying to me that I have to get that way....I HATE having to growl.
That's why I suggested having your husband deal with it. The boy would be more likely to listen to what he's told by your husband.
If you let him keep on behaving like that without challenging him, it will leave an impression on your boys. One possible outcome is that they will find his behavior acceptable.