But don't you want to be a part of a quality team? I think good companies, start with good leadership that gets filtered down. Part of the problem with society, is people not holding their own accountable to a higher standard. When you are both contractors for the same company, you should do your part to promote the culture that is at your company.
Plus, if getting him canned, means more potential freight lanes open for you, why not get rid of the riff raff?
That being said, I don't think appearance really makes a difference for the most part. We have a company standard and I often change out of my shorts into pants even though shorts are acceptable but 98% of the time, a $8 / hr docker worker isn't going to care what you are wearing.
The concept is good...that of drivers policing drivers. But, in reality, you have certain people that will be calling you in for wearing anything less than a tux. You can't depend on the driver population, as a whole, to make any kind of reasonable decision about each other. Just do YOUR job and do it well. Trust that those who don't do the same will find their own way out the door in one way or the other.