I'm really enjoying everyone's contributions to this thread.
Lawdog, I think you're exactly right that Tony's norms are so skewed that he really doesn't even see that these "ambitious" kids of his mob cronies could shoehorn AJ into the very life he believes would kill him.
On the other hand, there is a part of Tony, and in most fathers, that craves a child, especially a son, who will "follow in [his] footsteps". In this I'm mindful of a couple of David Chase interviews. Twice asked if Tony wants to keep his son out of the mob, Chase has answered, "That's what he says," clearly implying that that expressed desire may not tell the whole truth.
And Tony's words, even as far back as season 1, do suggest a modicum of duplicity on the point. Recall that, after seeing his father beat the crap out of a guy that owed him money, Tony bragged to his friends about "how tough his father was". Melfi asked if he was proud of his father after that beating and whether he thought AJ had a similar pride in him. Yes on both counts. And he further admitted that he was glad if his son was proud of him but that that was his dilemma because he didn't want AJ to BE like him.
If immitation is indeed the sincerest form of flattery, that admission itself shows a latent conflict of interest. He couldn't be entirely disappointed if AJ turned out to be a capable gangster because that would be the strongest indication of his own imprint on his son, the biggest stroke to his ego. On the other hand, he doesn't actively wish on him a life frought with the physical and emotional dangers a Mafioso faces, especially if AJ isn't equipped to conquer them.
So even though I think exposing AJ to the risks of fringe mob activity was not in his mind, perhaps that kernel of fatherly pride at the prospect of having a dual vocational/biological heir helped shape his negligent judgment.
hecatae, I understand your point that Tony may only intend to remain in therapy short term to help him deal with his own feelings over AJ's sudden suicidal mindset. I might be inclined to agree except that Tony specifically said he had to rescind his farewell to her and that he was now "trapped in therapy forever".
You could argue that that was hyperbole, but I think not so much. Tony spoke and acted as though he felt a duty to work on HIMSELF for AJ's sake. With much pain, he acknowledged that he is the cause of AJ's suffering, flying in the face of the ostensible truth about the ended relationship. And Tony's otherwise perplexing temper tantrum that "I fuckin' hate this shit!" and complaints that nothing ever really changes after all the tears and boredom and shooting the breeze in that office, sounded compellingly like the groans of a man who feels an obligation to do something unpleasant. And he wouldn't feel that obligation if he REALLY felt the problem was bad genes because he knows Melfi can't do a damn thing about that. He is right on the verge of admitting out loud that his life choices are what screwed AJ up. Once he does that, it's a whole new ballgame.
Tony, his spirits crushed after b-lining to the fridge first thing in the morning: "Who ate the last piece of cake?"