For me with a guy like Stafford I ask if his history is worth sacrificing Lock's potential. We know what Stafford is. We hope we know what Lock could be. If I'm the GM and I'm contemplating a move like that, I'm taking that in to consideration. If Dak, Watson, or Rodgers are available you pursue those guys because you hope that Lock is aware enough of what exactly those guys are and understand the move. Yeah, it would suck for Lock, but the GM's job is to put the team first and increase their chances of winning as much as possible.
"Milk is for babies. When you grow up, you have to drink beer" -Arnold