(Some of this discussion was inspired by a 2005 or 2006 Society of Biblical Literature presentation by Peter Head on the text critic Tregelles, of whom I have no first hand knowledge.)
Few people incur the wrath of KJV-onlyites as Wescott and Hort do.
Throughout the 19th century, scholars were studying the thousands of variant readings which were known to exist in the Greek manuscripts. As they studied the manuscripts and the readings, scholars realized that some manuscripts agreed with others more than others. When they sorted it out, they came to a general consensus that there were three (more or less) broad streams of related manuscripts.
One of those streams came to be known as the Byzantine text type which, by a fluke of history, claimed the most manuscripts, the vast majority of which were 12th century or later.
Previously, naïve students of the text of the Bible assumed that whichever reading could boast of the most manuscripts was most likely to be the original reading. This method, if it could be called such, made the place of the Textus Receptus, secure and made all (English) Bible believing Christians feel confident about their KJV.
However, the work of various scholars in the 19th century, and especially of Westcott and Hort, unraveled this confidence. Once they demonstrated that all those manuscripts of the Byzantine Text were simply the offspring of one of the three or four grandchildren of the original text, scholars realized that you can't just count manuscripts to determine the original reading.
In effect, Wescott and Hort overturned the discipline of textual criticism from a democratic election into a something more like a representative republic. To press the analogy, it would be like the state of West Virginia with its 3 million people getting the same number of representative votes as the State of California with its 20 million votes.
Consequently, whenever someone might point out to 200 Byzantine manuscripts with a given reading compared to one or two manuscripts from another text type, the response would be, "So what? We don't count manuscripts anyway. We weigh them." Thus, a large quantity of late manuscripts supporting one reading only shows that the reading of one variant reading produced more manuscripts which are currently extant.
This overturning of the basic (pseudo)-methodology of the Textus Receptus (~ Byzantine ~ KJV), then is one of the great legacies of Westcott and Hort, and this is the reason why they are hated so much by KJV-onlyites. But there's more to the story….
KJV-onlyites rarely are capable of attacking Westcott and Hort on methodological grounds. The reality is, few of them are capable of reading Hort's famous introduction. Consequently, the attack against Westcott and Hort is almost entirely ad hominem. In particular, Hort is attacked for things like rejecting inspiration, or maybe even high doctrines like the Trinity…, whatever. (Apparently, little is known about Westcott's own personal life.)
Actually, KJV-onlyites know only one or two things about Hort, but their rhetoric gets fanned into ever increasing inflammatories and deprecations.
But now, the record needs to be set straight!
I'm not going to defend Hort. Say what you may.
However! Let me tell you about an Englishman named Tregelles. Apparently, Tregelles was a devoted believer, deeply involved in the Brethren movement which continues to be Great Britain's equivalent of American Fundamentalism, albeit gentler. He was known for his personal piety and theological orthodoxy.
Tregelles was not famous like Cambridge professor Hort was, even though Tregelles was older. Tregelles had been working on his own edition of the Greek New Testament, being well ahead of Hort. But the two men struck up a serious camaraderie, resulting in Tregelles sending Hort his edition and notes on the Greek New Testament as each page was written.
To be sure, Hort was critical of Tregelles for his firm belief in scripture, but Hort was impressed by Tregelles' work. In fact, Tregelles had a huge impact on Westcott and Hort's New Testament. A comparison of Tregelles' text to Westcott and Hort's text would see a characteristic similarity between the two.
Scholars are in the habit of referring to the Standard Text (i.e., Nestle-Aland's critical text) as the Hortian text. In reality, however, perhaps we should speak not so much of the Hortian text, but of the Tregellian text!
With all this background information, it seems that we can all dispense with the vicious attacks against Hort for his liberalism. KJV-onlyites might be able to make hay, so to speak, by attacking Hort, but in reality, Hort's text was largely derived from a seriously devoted believer who was committed to biblical inspiration, theological orthodoxy, and holy living.