What did classical guitarists think about the electric guitar when it first arrived and started getting popular?

I'm not a historian as such, but I have a Ba(Hons) in Popular Musics and my largest final year piece of work was an in depth presentation and look at the technological development of the electrical guitar (Though I did extend my focus several decades beyond that required to write the following), so I may well have something to say on this -

As far as I am aware, there was never really much of a response that I'm aware of from the classical guitarist community. (Edit: The comment above makes note of Segovia specifically. I'm sure his opinion is genuine but I suspect, as the other comment notes, Segovia's opinion may be more to do with him being a crotchety old man, rather than a mouthpiece for classical guitarists everywhere)

The reason is probably that there had already been a significant split from other guitarists anyway - Steel strung guitars made by companies like Martin had been in production since the early 20s and were already very popular. When the time came to electrify or further amplify these instruments, it wasn't the sound of a nylon or gut-strung guitar that they were seeking to amplify - it was the sound of the steel string.

The earliest patent awarded to this end is US Patent 2020577, to Lloyd Loar, then of the Acousti Lectric Company. http://www.google.co.uk/patents/US2020557

The earliest instruments to use this system actually predate the patent by some time - Gibson's website claims Loar tried to interest the company in his idea as early as 1923, but in practice he failed to achieve their support and ultimately the first electrified instruments didn't appear until 1928, in the form of a Resonator built by the Stromberg-Voisinet company, or the rather more famous than either of these, "Rickenbacker Frying Pan" of 1931, which while very guitar-like, is actually a Lap Steel.

Loar's idea would have worked with nylon strings, but Steel strings are capable of holding much higher tension and would have been much better when used with Loar's idea - a fairly simple transducer arrangement which directly utilised the vibration of the bridge and soundboard to drive an electromagnetic transducer located in a compartment under the bridge and connected by an armature that could be raised and lowered in order to engage or disengage the bridge from the soundboard or transducer (or adjusted to be in contact with both, providing both acoustic and electric volume).

Ultimately Loar's Vivi-tone electric guitars were comparitively unsuccessful, and only went on sale in the early 1930s - 1933 is the earliest date I've seen for one, and his patents were filed in 1934 and awarded in 1935 for the Vivi-Tone pickup/Transducer system.

Gibson introduced a similar idea of their own at around the same time to much greater success, with the L-1 and L-00 guitars, but despite those being successful by the standards of the time, the real winner of this period, and the first guitar to come with an electric pickup as standard rather than an option, is the ES-150, made famous by Charlie Christian and first produced in 1936.

At this point in time, the modern electric guitar pickup, and it's sound, is essentially complete - it's a coil of wire wrapped around a ferrous core with magnetism provided by (very large, by modern standards) Samarium Cobalt magnets affixed to the bottom of the steel core. The ferrous metal strings excite the magnetic field and induce a voltage in the coil, that voltage is then fed to an amplifier, and voila. The electric guitar pickup is born.

I could go on at length about subsequent developments in pickup design but that would stray from the question - the ES-150 proved to be a very successful instrument with one major drawback - it was, like all hollowbodied amplified instruments, susceptible to feedback at high volumes - a problem that would plague musicians until Les Paul created his famous "Log" and the Gibson and Fender guitar companies released the first two production solidbody electric guitars in 1952 - the Les Paul, and the Telecaster (Originally known as the Broadcaster, then without branding after a legal challenge by Fred Gretsch, whose company marketed a drumkit with the same name, and finally the Telecaster)

But ultimately, that ES 150, like the L-1 and the L-00 before it, the Frying Pan and the Vivi-Tone before it, all started with the steel strung guitar as their base, not the gut-strung classical guitar or flamenco guitar.

As a result, there really wasn't much reason for the classical guitarists to form an opinion - if amplified at all, they were typically using the same technologies acoustic guitars are amplified with today - Piezoelectric elements placed under the saddles, which offer a much more natural sound and don't rely on the strings being made of a ferrous material to work - something that would have been anathema to a musician interested in playing flamenco or classical music, as steel strings simply sound too bright, brash and jangly for their repertoire!

By the time 1952 rolled around and the solidbody electric guitar as we know it comes into being and starts selling in quantity, there's been at least a decade and a half of Charlie Christian as one of the most visible electric guitar players around, and lots of ES-150s sold, all strung with steel.

The idea of amplifying acoustic instruments at that point would have long branched off into it's own area, much as it is today, with companies like L.R.Baggs focusing almost entirely on acoustic amplification, trying to preserve the natural sound of the instrument, while electric amplification was already it's own independent thing, with Les Paul leading the charge and continuing to invent and promote new electric ideas such as Multitrack recording, etc, that simply didn't apply to nor impinged upon the qualities classical players appreciated in their instrument of choice.

Sources - http://www.gibson.com/News-Lifestyle/Features/en-us/Electric-Harp-Guitar-201.aspx

https://www.vintageguitar.com/3657/stromberg-electro/

https://en.wikipedia.org/wiki/Vivi-Tone#cite_note-3 (I no longer have access to the library I used when I researched this, but Wikipedia cites two books and page references for this claim)

Duchossoir, A.R.; Wheelwright, Lynn (March 2012). "The Original ES-150: How Gibson Won the ES-War, Part 1". Vintage Guitar.