I do not know whether or not to use the names now or not. In court, there is no way any of these folks could win a case, but they could make my life very hard.
1. Plagiarism would be if you used their quotes or ideas and then tried to pass them off in your book as your own. So, that does not appear to be an issue here since you are critiquing their quotes. Copyright laws, however, protect a writer's words as his legal property. So, normally to use their quotes you would not only have to identify the author but also get the author's permission to use it unless there exists a legal exception such as "fair use". Quoting another's work for purposes of review or criticism typically qualifies as a fair use exception to copyright infringement.
I also do not know if an LLC would be any protection to me personally in this case.
2. The other concern we discussed is a defamation suit. If you say something about a person that is NOT TRUE and is likely to harm their reputation, then you could be held liable for defamation.
In Texas the elements of a defamation claim are
(1) The defendant published a statement;
(2) The statement was defamatory concerning the plaintiff;
(3) The defendant acted with
(i) actual malice, if the plaintiff was
a public official or public figure, or
(ii) negligence, if the plaintiff was a
private individual, regarding the truth
of the statement
WFAA-TV, Inc. v. McLemore, 978 S.W.2d 568, 571 (Tex.1998).
“Defamation” takes two forms: libel and slander. Slander is a false oral statement that is published to a third person without a legal excuse, which refers to an ascertainable person. Randall's Food Markets. v. Johnson, 891 S.W.2d 640, 646 (Tex.1995). Libel is written or printed defamation.Rogers v. Dallas Morning News, 889 S.W.2d 467, 472 (Tex.App.-Dallas 1994, writ denied).
NOTE: Because a statement must be false to be defamatory, an opinion itself cannot form the basis of a defamation claim because it cannot be proven true or false.
An LLC will not shield you from being personally liable for a tort such as defamation.