This is a classical case of taking things out of context.
Let's explain the whole story:
1) The Lubavitcher Rebbe zt"l felt that it is better for woman to wear a shietel the wear a tichel, because those who wear a tichel are often not careful about covering all their hair.
2) The Rebbe was speaking to his Kehila which he knew well, and was obviously not talking to communities like Satmar etc. where women a) often shave their hair and b) the tznius is already on a higher level and women have less of an issue keeping to higher standards, therefore this is less of a chashash that a womean with a tichel will leave hair uncovered. [Here is not the place to discuss the historical/sociological differences of communities that come from Hungery vs. those that come from Russia and also have many BT's etc. and the effect that this has on the Tznius standards].
3) Indeed, in Chabad, those women who leave their houses with tichels and not sheitels, are almost always not "super frum" and are leaving much hair uncovered, thus not covering their hair properly according to Halocho.
4) The new Rav of Kfar Chabad (Rav Meir Ashkenzy), who happens to be an exceptionally honest and fine person, has taken it upon himself to fix the Tzniuts standers of Kfar Chabad. One of his campaigns are to stop the trend of women leaving their house with a tichel only half covering their hair, and instead enforcing the Rebbe's shito, that in Chabad women should leave their house with a sheitel, so that their hair will be fully covered.
5) In order to explain how important it is to cover one's hair fully, Rav Ashknazy quoted to some women the Halocho the a man must divorce his wife is she does not cover her hair. in other words - he was telling the women, don't look at this sheitel vs. half covered hair with a tichel as a light issue, it is a very serious one, as not covering hair is a reason for divorce.
6) the Rav NEVER told any man or women, that they should get divorced because the woman left her house with a tichel. that is a complete lie.
7) some of the more modern women of Kfar CHabad, who are not so happy with the fact that the Rav is enforcing Tznius standards in the Kfar (as a Rav should do), went to the press, and quoted him completly out of context - as saying that a man should divorce his wife if she wears a Tichel.
סערת איסור המטפחות בכפר חב"ד: רבני חב"ד נגד פסק הרב אשכנזי: "לא צריך לגרש את האישה"
חובה על הבעל לגרש את אשתו אם היא חובשת מטפחת ולא פאה? רבנים בכירים בחב"ד מתייחסים לסערת הרב אשכנזי וקובעים: "אפשר לשכנע, לא צריך להגיע עד לגירושין בגלל וויכוח כזה" (חרדים)