I'm the first to agree that lawyers are not paragons of virtue. But most of us try and abide by both the letter, and the spirit, of the law. This is particularly so when it comes to our ethical obligations. It is a violation of the Model Rules of Professional Responsibility to date a client while that person is still your client. Unless you were intimate prior to the commencement of the attorney-client relationship, it is verboten to engage in hankus pankus thereafter.
There's just something about the whole scenario that makes you go 'ick.' It's degoutant, as the French would say (although as I noted earlier, there's not much these days that seem to disgust the French.)
That's why I have a hard time feeling any sympathy, let alone solidarity, with Jennifer Mitrick the amazingly still-employed Philadelphia ADA who allegedly had an inappropriate relationship with the victim in one of her drug cases.
The fact that the victim was an alleged (snicker, snicker) drug dealer just makes it worse.