Why would rooted users be more at risk? If anything someone who has rooted a phone should be more aware of what he's downloading into the phone. Further, within the community itself applications for rooted owners are pretty well scrutinized.
Root access of a phone allows any app access to the base software on the phone. As such, being rooted increases the risk to the phone. However, your next point is very true. Therefore rooted phones are more at risk but your average rooted user is far less likely to engage in risky behavior. Now, there are dunces on both sides of the fence, but overall I'd bank on rooted users
on the whole being safer Droiders.