about a bit of Thanksgiving Latin

In one of my increasingly infrequent rambles in the blogosphere, I recently came across this page:
http://vaviper.blogspot.com/2012/11/a-thanksgiving-miscellany-mark-twain.html
on which, among other things related to the Thanksgiving theme, there is a quotation attributed to Cicero, viz:

Gratius animus est una virtus non solum maxima, sed etiam mater virtutum omnium reliquaram.
- Marcus Tullius Cicero (106-43 B.C.) (Oratio pro Cnaeo Plancio, 23)

(A thankful heart is not only the greatest virtue, but the mother of all other virtues.)

The Latin is grammatically or morphologically flawed in two respects ("gratius" and "reliquaram" - perhaps these are just spelling errors), the line or paragraph number is wrong, and the quotation itself is not exactly what Cicero wrote (or said).

The quotation may have been lifted from this page, or one like it:
http://orbiscatholicussecundus.blogspot.com/2012/11/rome-quotes_23.html

That in turn seems to have been transcribed inattentively from something like this:

Gratus animus est una virtus non solum maxima, sed etiam mater virtutum omnium reliquarum.
  A thankful heart is not only the greatest virtue, but the parent of all the other virtues.
        Cicero—Oratio Pro Cnæo Plancio. XXXIII.

from perhaps this page (Hoyt & Roberts, comps.  Hoyt’s New Cyclopedia of Practical Quotations.  1922, at Bartleby.com), or maybe this one: The cyclopaedia of practical quotations: English and Latin; with an appendix. . . (1894)

What Cicero actually wrote, in chapter XXXIII, section 80, goes like this (from the Latin Library):

etenim, iudices, cum omnibus virtutibus me adfectum esse cupio, tum nihil est quod malim quam me et esse gratum et videri. haec enim est una virtus non solum maxima sed etiam mater virtutum omnium reliquarum. quid est pietas nisi voluntas grata in parentes? qui sunt boni cives, qui belli, qui domi de patria bene merentes, nisi qui patriae beneficia meminerunt? qui sancti, qui religionum colentes, nisi qui meritam dis immortalibus gratiam iustis honoribus et memori mente persolvunt? quae potest esse vitae iucunditas sublatis amicitiis? quae porro amicitia potest esse inter ingratos?

The "gratus animus" seems to have been a distillation of the initial sentence to a noun phrase representing the quality to which it refers, and that was then substituted for the pronoun "haec" in the second, an operation performed presumably by some 19th century compiler of notable, memorable, and therefore quotable expressions.  The resultant statement is not really Cicero's, but would qualify as a fair representation of his idea about gratitude, at least as that was conceived in the first century B.C.

It's not easy for me to comment about a phenomenon like the appearance of this quotation in a modern blog.  On the one hand, one could say that it's nice to see Latin in current use.  On the other, one could also say that it's a bit disappointing to see mangled Latin in current use.  On the whole, I suppose it reflects rather poorly on current ideas of high quality education and high quality writing that a writer doesn't really understand the Latin he or she cites and is unable or unwilling to run a quotation noted in some sort of compilation down to its source so as to verify such things as its accuracy, legitimacy, context and aptness for the contemplated use.