In response to "His own followers said that Luther was a pathological liar, his teaching bore this out; hence, Falsus in uno, falsus in omnibus.".
While Dr. Johann Eck wasn't a follower of Luther He did say a few things of Luther's character:
“More than once have I proved,” he says, “ that he is a liar and hence that he has for his father, him [the devil] of whom the Scripture says that he is a liar and a murderer.” “The fellow exudes lies from every pore and is inconstancy itself (homo totus mendaciis scatens nil constat). His teaching too is full of deception and calumny. What he has just advanced, he presently rejects without the least difficulty.” “ The dregs of those vices of which he is always accusing the Christians, we rightly pour back upon his own head ; let him drink himself of the cup he has mixed.” “ He heaps up a mountain of evil on the Pope and the Church,” but with “ his nun,” this is what he adds in a later edition in his indignation with Luther s marriage “ he is really worshipping Asmodeus “ and this he is not ashamed to do in the old monastery of the Augustinians, “ where once pious monks served the Lord God, and pious foundations, now alienated from their original purpose, proclaimed the Christian virtues to the faithful.” [Hartmann Grisar, Luther, pg. 147 c., Conclusion of the Tract “De Purgatorio,” “ Opp.,” Pars II, Ingolst., 1531, pp. 95 , 96. Cp. volume iv., xxii. :” Luther and Lying.”]
And then there was Thomas Müntzer, a reformer's reformer.
[Thomas] Müntzer, in his “Schutz Rede,” was not slow to answer Luther’s “boasting “concerning his three appearances in public. It must be touched upon here for the sake of completeness, although it must be borne in mind that it is the utterance of an opponent. Müntzer calls Luther repeatedly, and not merely on account of this boasting, “Dr. Liar “and“ Lying Luther.” He says to him: “ Why do you throw dust in the eyes of the people ? you were very well off indeed at Leipzig. You rode out of the city crowned with gillyflowers and drank good wine at Melchior Lother’s? Nor were you in any danger at Augsburg [as a matter of fact every precaution had been taken], for Staupitz the oracle stood at your side. . .. That you appeared before the Empire at Worms at all was thanks to the German nobles whom you had cajoled and honeyed, for they fully expected, that, by your preaching you would obtain for them Bohemian gifts of monasteries and foundations which you are now promising to the princes. [Hartmann Grisar, Luther, pg. 367, c., In “Neudrucke”; this work also is edited by Enders (p. 19 ff.). The passage will be found on p. 37 f.]
And
Here comes Campanus, he says of a refractory theologian in his ranks, and “ makes himself out to be the only man who is sure of everything” ; “he prides himself on being certain upon all matters and of never being at a loss “ ; Campanus condemns him as a “ liar and diabolical man,” and of this he was “ as sure as that God is God.” And yet this Campanus has “ never passed through any struggle, nor had a tussle with the devil, and actually glories in the fact.” On the other hand, he himself, he says, had been “ tried by the devil “ and proved by “ temptation “ ; that is the true test and is essential for every real “student of theology” ; “for as soon as God s Word dawns upon you, the devil is sure to try you, and in this way you become a doctor in very truth.”[Ibid, pg. 378]
