So you don’t have any actual reference to polygamy actually being an practiced by Christians, and it being acceptable?
Not the Catholic Church, no, however it does appear (and I am using a Wikipedia article, but it seems to be one that is documented
en.wikipedia.org/wiki/Polygamy#_note-6)), that Luther at least at one point did not consider it a major problem:
"Periodically, Christian reform movements that have aimed at rebuilding Christian doctrine based on the Bible alone (sola scriptura) have at least temporarily accepted polygamy as a Biblical practice. For example, during the Protestant Reformation, in a document referred to simply as “Der Beichtrat” ( or “The Confessional Advice” ),[5] Martin Luther granted the Landgrave Philip of Hesse, who, for many years, had been living “constantly in a state of adultery and fornication,”[6] a dispensation to take a second wife. The double marriage was to be done in secret however, to avoid public scandal.[7] . Some fifteen years earlier, in a letter to the Saxon Chancellor Gregor Brück, Luther stated that he could not “forbid a person to marry several wives, for it does not contradict Scripture.” “Ego sane fateor, me non posse prohibere, si quis plures velit uxores ducere, nec repugnat sacris literis.”[8]
“On February 14, 1650, the parliament at Nürnberg decreed that because so many men were killed during the Thirty Years’ War, the churches for the following ten years could not admit any man under the age of 60 into a monastery. Priests and ministers not bound by any monastery were allowed to marry. Lastly, the decree stated that every man was allowed to marry up to ten women. The men were admonished to behave honorably, provide for their wives properly, and prevent animosity among them.” Larry O. Jensen, A Genealogical Handbook of German Research (Rev. Ed., 1980) p. 59 [24]. See also Joseph Alfred X. Michiels, Secret History of the Austrian Government and of its Systematic Persecutions of Protestants (London: Chapman and Hall, 1859) p. 85 (copy at Google Books), the author stating that he is quoting from a copy of the legislation. But see William Walker Rockwell, Die Doppelehe des Landgrafen Philipp von Hessen (Marburg, 1904), p. 280, n. 2 (copy at Google Books), which reports the number of wives allowed was two. And contrast Leonhard Theobald, “Der angebliche Bigamiebeschluß des fränkischen Kreistages” “The So-called Bigamy Decision of the Franconian Kreistag”], Beitrage zur Bayerischen kirchengeschichte [Contributions to Bavarian Church History] 23 (1916 – bound volume dated 1917) Erlangen: 199-200 (Theobald reporting that the Franconian Kreistag did not hold session between 1645 and 1664, and that there is no record of such a law in the extant archives of Nürnberg, Ansbach, or Bamberg, Theobald believing that the editors of the Fränkisches Archiv must have misunderstood a draft of some other legislation from 1650). See also Alfred Altmann, “Verein für Geschichte der Stadt Nürnburg,” Jahresbericht über das 43 Vereinsjahr 1920 [Annual Report for the 43rd Year 1920 of the Historical Society of the City of Nuremburg] (Nürnberg 1920): 13-15 (Altmann reporting a lecture he had given discussing the polygamy permission said to have been granted in Nuremberg in 1650, Altmann characterizing the Fränkisches Archiv as “merely a popular journal, not an edition of state documents,” and describing the tradition as “a literary fantasy”)."
Now whether you as a Catholic are willing to admit that the teachings of Luther represent any sort of accurate Christian teachings or not is quite another question, but he is certainly regarded as a major Christian theologian by the general populace.
