Professional ethicists aren't any more likely to behave ethically than baseline humans who don't get paid to sit around all day and contemplate the difference between right and wrong.
There are some pretty good arguments for not expecting ethicists to behave ethically, along the lines of, "If you can claim to be an ethicist if your behavior is as good as your philosophy, then ethicists will be incentivized to come up with moral justifications for bad behavior, rather than rigorous, intellectually honest arguments for good behavior." It's a version of the argument that "All countries fall short of their stated principles, but the principles America falls short of are better than most."
The moral philosophers whom we remember from the past — Socrates, Buddha, Jesus — lived as they preached, and much of the moral authority of their teachings comes from their willingness to sacrifice their own comfort for their beliefs (washing beggars' feet, drinking hemlock).
Eric Schwitzgebel surveyed a sample of ethicists and determined that contemporary moral philosophers are no more likely to live a "good life" by their own lights than anyone else — though they do define a good life with more rigor than the rest of us.
An ethics professor teaches Peter Singer's arguments for vegetarianism to her undergraduates. She says she finds those arguments sound and that in her view it is morally wrong to eat meat. Class ends, and she goes to the cafeteria for a cheeseburger. A student approaches her and expresses surprise at her eating meat. (If you don't like vegetarianism as an issue, another example could serve: marital fidelity, charitable donation, fiscal honesty, courage in defence of the weak.)
'Why are you surprised?' asks our ethicist. 'Yes, it is morally wrong for me to enjoy this delicious cheeseburger. However, I don't aspire to be a saint. I aspire only to be about as morally good as others around me. Look around this cafeteria. Almost everyone else is eating meat. Why should I sacrifice this pleasure, wrong though it is, while others do not? Indeed, it would be unfair to hold me to higher standards just because I'm an ethicist. I am paid to teach, research and write, like every other professor. I am paid to apply my scholarly talents to evaluating intellectual arguments about the good and bad, the right and wrong. If you want me also to live as a role model, you ought to pay me extra!
'Furthermore,' she continues, 'if we demand that ethicists live according to the norms they espouse, that will put major distortive pressures on the field. An ethicist who feels obligated to live as she teaches will be motivated to avoid highly self-sacrificial conclusions, such as that the wealthy should give most of their money to charity or that we should eat only a restricted subset of foods. Disconnecting professional ethicists' academic enquiries from their personal choices allows them to consider the arguments in a more even-handed way. If no one expects us to act in accord with our scholarly opinions, we are more likely to arrive at the moral truth.'
'In that case,' replies the student, 'is it morally okay for me to order a cheeseburger too?'
'No! Weren't you listening? It would be wrong. It's wrong for me, also, as I just admitted. I recommend the avocado and sprouts. I hope that Singer's and my arguments help create a culture permanently free of the harms to animals and the environment that are caused by meat-eating.'
(Image: Cheeseburger, National Cancer Institute, Public Domain)