I'd rather see Franzen knee someone in the head, then throw a fit when someone touches glove to his face. Do enforcers prevent injuries? No, but they prevent reoccurring instances where the entire team gets bullied, thus leading to injuries. Enforcers are the street justice of the hockey world. The "police" (refs) aren't doing an adequate job for the most part in supporting player safety, so that's where the thugs come in. Is it really that hard to acquire someone that can fight AND play hockey? Probably not..
Edit: Having players with multiple roles seems to be non existent.