That is a little like saying people who teach music don't claim to play an instrument very well. Universities are full of professors who can't do the thing they teach about very well. But I think we should be skeptical of people who study a thing they can't practice.
You can be skeptical all you want of ethics/morality as a field of academic research! I think there are some good reasons to be. That doesn’t mean the researchers are hypocritical when they sometimes act immorally (as all inevitably will on account of being humans), or that it’s ironic or whatever.
If you showed the same obviously unethical act to both a layperson and an ethicist and asked them, purely as a thought exercise, to present a collection of ethical justifications for what they saw the ethicist would almost certainly have an easier time doing so and would produce arguments which were more convincing (at least to ethicists) due to their familiarity with accepted frameworks.
It might be reasonable to guess that as a consequence ethicists overall may have a greater capacity for unethical conduct than arbitrarily selected members of the public (controlling for other factors).
Teaching in itself - understanding a complex topic and communicating to newbies - is a skill that is independent of the ability to do the thing.