If we say that moral philosophy in one sense undermines and endangers the common morality of a given society, then it could sound as though the moral philosopher exists at a lower level of moral obligation.
It might sound as if the moral philosopher looks at the morality of the herd and laughs with derision, prancing around gaily from injustice to vice and back, never bound by any of the socially imposed chains of decency or goodwill or moderation that normally prevent us from committing whatever evils might enter our thoughts.
And indeed, there are some who have spent time in philosophical activities who can arrive at precisely this conclusion. The philosopher is the secret amoralist, they feel, who in a moment of necessity could commit perjury as easily as cooking an egg.
Still, in my experience this is a comparatively rare outcome. More commonly (and, in my considered opinion, more reasonably), people who spend time genuinely giving thought to moral philosophy end up holding themselves more rigorously to a moral standard.
I wonder if partly this is just because the philosophical soul has more of a tendency to think things through to their logical conclusion, and so can almost instinctively recognize the danger of excusing small injustices. I’m not necessarily thinking here of a vice like overindulging in guilty pleasures; probably, someone with philosophical training is generally just as likely as the next person to eat more chocolate than is wise, I’m afraid.
Still, I do think that there is a moral courage that very frequently arises from the study of moral philosophy. Having thought through moral questions and surveyed possible answers and arrived at well-founded conclusions through hard work, the thoughtful person becomes, certainly not incorruptible, but more willing to work and to sacrifice and to suffer for those convictions.
At the beginning of the philosophical task, a person must be willing to tear down inherited beliefs, not because they are known to be untrue but because they are known to be built on an unphilosophical foundation for that particular person. This is a dangerous process, since many are unequipped for the task of building up afterwards and so they get stuck partway and fall back on some of their inherited beliefs but not others, thinking they’ve done something wise but living as fools; and even among those who are equipped to go further, there are some few who will stop at this point anyway, for one reason or another. However, for all who make it through this initial phase of seeking to abandon opinion and pursue knowledge, there remains the question of the self, the seeker, the soul — the human person. The philosopher is a moral being in a particularly intense and unique way.
In my view, it is one of the best aspects or effects of the philosophical undertaking.