Of course some lawyers DO use DR. Perfectly legit.
http://www.abajournal.com/magazine/article/lawyers_are_doctors_too/
The use of the honorific “Dr.” is especially useful in Dr. Titus’ case, as he is a professor of law, and has practiced law at higher levels of professional standing than most lawyers.
Your link actually confirms that the profession largely rejects the honorific title “Dr.”
A JD lawyer who uses “Dr.” invites the ridicule of the academy and the profession.
It is similar to a person with an honorary doctorate - they technically can use the title “Dr.” but if they do they invite ridicule.
As a practical matter, it is NOT legit.
Even the deans of Yale and Harvard Law who are JDs don’t use the title “Dr.”
As a practical matter, there is no “higher level” or academic status that legitimizes the use of “Dr.” by a JD.
No self-respecting JD (who does not also have an MD or PhD) a uses the title “Dr.” Its not done.
Or, others referring to him as "Dr."?
It appears that, elsewhere, he's referred to as "Mr." or "Esq."
Herbert W. Titus is of counsel to the law firm of William J. Olson, P.C. Prior to his association with this firm, Mr. Titus taught constitutional law, common law, and other subjects for nearly 30 years at five different American Bar Association approved law schools. From 1986 to 1993, he served as the founding Dean of the College of Law and Government in Regent University, Virginia Beach, Virginia. Prior to his academic career, he served as a Trial Attorney and a Special Assistant United States Attorney with the United States Department of Justice in Washington, D.C. and Kansas City, Missouri. Today he is engaged in a general practice with a concentration in constitutional strategy, litigation, and appeals.William J. Olson, P.C. - Attorneys At LawMr. Titus holds the J.D. degree (cum laude) from Harvard and the B.S. degree in Political Science from the University of Oregon from which he graduated Phi Beta Kappa.
...
Furthermore, it appears that a book authored by him, doesn't use the title. [1][2]
Additionally, some terminology on the various law degrees, in particular:
The term "Doctor of Law" refers to the degree of Juris Doctor (JD), which in the U.S. is the only first professional law degree,[20][21][22][23] and to the S.J.D. (Scientiae Juridicae Doctor or J.S.D., the degree name in English or Doctor of Juridical Science).[22][24] The S.J.D. is the research doctorate in law, and as such it is generally accepted as comparable to the more commonly awarded research doctorate, the Ph.D.[25] The S.J.D. is described as the "highest degree in law" by the University of Virginia,[26] the "terminal degree in law" by Indiana University[27] and Harvard Law School [28] and as the "most advanced law degree" by Yale Law School,[29] Georgetown Law,[30] New York University [31] and Stanford University.[32] The National Association of Legal Professionals states that the J.S.D./S.J.D. is "typically the most advanced (or terminal) law degree that would follow the earning of the LL.M. and J.D. degrees."[33] However, while the degree may be the highest research doctorate in law, the J.D. is also a doctorate (the highest professional doctorate in law),[34] as evinced by universities' description of the S.J.D. as a a "postdoctoral degree."[32][35] The American Bar Association has issued a Council Statement[36] stating that the J.D. be considered as being equivalent to the Ph.D. for employment and educational purposes.[37] The S.J.D. typically requires three to five years to complete, and requires an advanced study in law as a scientific discipline and a dissertation, which serves as an original contribution to the scholarly field of law.[38]
While it may be "socially unacceptable" in some circles, for a JD (Juris Doctorate) to refer to themselves with the "Dr." title, technically...they would be correct.