Lorraine Bracco's role in particular is a positive one: Melfi's quite consciously meant to be a moral counterpoint to Tony's gangsterism.
I didn't find Melfi to be that likable, honestly. Just because someone's not a criminal doesn't mean they're sympathetic or likable. Actually I found Tony much more likable than she was! Her dumping (as a patient, of course) of Tony in "The Blue Comet" was unprofessional and downright cowardly. She didn't have the guts to tell him what was really bothering her (the study she had read about), so she provided completely bogus reasons for dropping him as a patient. It was a really shitty thing to do.
Melfi's professional competence might be questionable, but that she's 'made it' as a Doctor - something that Tony himself is in awe of throughout the show - is enough to put her in the 'positive representation' category alone. I never said she's likeable or sympathetic (though I'm not saying she isn't); I said her role is a positive one.
Additionally, I didn't admire that she didn't tell Tony about being raped. And to those who say she did the "moral" thing, remember that this man could easily haved raped (or killed) another woman in the future. If your daughter was raped and/or murdered, and you learned that Melfi could have prevented it by telling Tony what happened to her and who did it, you would hardly think she did the right thing by keeping quiet.
So Tony's capacity for violent retribution, outside the confines of not only the legal system but general human morality, is something to admire and respect?
If Tony kills Jesus Rossi, he's hardly struck fear into the hearts of all of society's rapists; it should go without saying that 'one more dead' isn't any kind of feasible way to deal with something as socially destructive as rape, nor is it any way to support its victims.
Moreover, why for that matter would we not 'disown' Tony for refusing to kill Ralphie right after the latter brutally murders Tracee? There's little logic to your argument.
Why does Melfi have to tell Tony for Rossi to get his 'comeuppance'? She could have pursued it in any way she pleased once she saw Rossi's face on that 'Employee of the Month' card.
It's presented the way it is because Chase and his writers have point-of-view on their side; the show is framed through Tony's viewpoint, and it can be quite appealing to then see events through his moral outlook.
