That isn't true, but enough fall short and get exposed that it taints the rest in the eyes of at least some of the public.
My personal experiences, yes, it is true.
My opinion is anecdotal, based on the partners and associates of one of the top law firms in DC and the government disability offices, both places where I know lawyers working within, it is indeed true, most have far less moral and ethical fiber than a paycheck-to-paycheck prole.
You make your argument, your opponent makes his, and whoever persuades a jury or a judge wins.
Whether you argument is logically correct, meets the facts or the law, or is just is completely irrelevant apart from whether the judge or jury finds you persuasive.
The fact that we, as a society, turn over so much authority to people trained to be paid liars is a big problem.