Yes, the focus of this episode is on impulse control and the lack thereof. Joel correctly points to the necessity of a patient's being able to control his or her urges in order to benefit from talk therapy. At the same time, we all realize that this requirement is paradoxical if not somewhat lame, in that so many of our patients come in to be treated for that very incapacity.
I will once again come down harder on the therapist than my colleagues, I suspect, in saying that Jennifer's apparent success at helping Tony acknowledge the "inappropriateness" of his outburst was obviously too little, too late. While it wouldn't have worked miracles, Jennifer should have established a much firmer frame and ethos for the therapeutic relationship from the start. By this point in the treatment, Tony should have known that his therapist would never discuss another patient or ex-patient with him, that his therapist wouldn't accept a floral delivery without analyzing its meaning immediately, and that menacing behavior in the session would be thoroughly explored and contained as soon as possible, not several weeks' hence. Tony doesn't know this because Jennifer hasn't shown this by example. I'm speculating that if she had been able to infuse a greater sense of "the code of treatment," it would have given Tony a new and different model for moral, mutually protective and respectful functioning. Having said this, I admit that it would be extremely difficult to achieve this with a patient like Tony, who would put all his efforts into subverting that code.
Holding the mirror up to the underbelly of human nature, the writers appear to say that destructive, greedy impulses can be sublimated—that is, put toward pro-social uses—only temporarily. When efforts to do good aren't sufficiently effective (or sufficiently rewarded?), people readily sink back into selfish avarice and justify it with embittered attacks on the system. While a wiseguy can behave well in locker rooms doing business deals (that is, when flexing his muscles), the childish, aggressive impulses take over once his longing gets triggered by a soulful lament. If that's the writers' view, they're entitled to it—but is it truth, or just a sardonic image of humankind meant to demoralize the episode's viewer?