Well even better, don't think in Good Guy/Bad Guy terms.
Think of it as "who you're allied with". Every charachter has its own agenda, and you decide which one suits your own needs.
Think of it this way.
You live in post-apocalyptic Las Vegas. Maybe you have a family now, a life, and simply want to get by. Now, you work for a group of casino owners on the Strip. You know they aren't exactly humanitarians, but they provide you with the security you and your family need.
Often, you are tasked with dealing with people who go against your employer's best interests. Sometimes its a group of raiders, sometimes its that little Mormon church down the street. Sometimes, you know almost nothing about them.
You are told to kill this messenger and take what he has. No questions asked. Wouldn't you? Its either him, or you.
This probably isnt the case for Benny, but its still something to think about. I think Benny falls into the opportunistic ruthless thug category. But, ya never know.