OK, I didn't read the whole thread yet, though I'm going to as I find this topic very interesting, but I couldn't resist simply posting an answer to the original question. It's gonna be small novel, sorry about that...
It is hard to define whether I'm a purist because within the confines of this site, the word purist has a little different meaning. There are some real purists here; people who out of principle would rather watch a crappy LD transfer or an old VHS then an HD version with a few minor changes and I have a great respect for that but obviously I'm not one of those people, so I'm not a purist that sense or in the sense that I'd think the original should be the only version; there are plenty of other films where I actually prefer the altered versions/director's cuts (eg. LOTR TTT or Aliens) but I'm very happy that I can watch the originals in the same or comparable quality.
I am however a purist in that I think that any official release of an unaltered version should be really absolutely unaltered beyond some basic cleanup. I actually hate the idea of a version that wouldn't have all the most obvious changes but have the "invisible" fixes such as recompositing or removing wires etc. An official release like that to me would be more offensive than an obvious Special Edition, unless again it would have the original original alongside it.
This goes for other films as well; it bothers me that in the BD of Aliens they removed the hole in the ground where Bishop's real body is hiding or that they removed the cobra reflection from the Raiders Blu Ray. It doesn't bother me to a point where it would taint my enjoyment of the movie because they are small changes but it does bother me.
So I guess I do consider myself a SW purist in the sense that I very much wish the original version was released officially in an absolutely unaltered form.
And now when and why I became such: I first saw the original SW film on TV when I was very little in the early 90s and I loved it but remembered very little of it. Then later I got the original on a copy of a copy VHS and had that for years even after the SE came out. I later got the 97SE trilogy on VHS, so I only saw the SEs of ESB and ROTJ. The original versions of all 3 films were nearly impossible to find in the Czech Republic (though they did come out but they weren't for sale anywhere anymore and none of the VHS rental places in my town had them).
Then one day, when I was like 12 we went to visit my aunt and uncle in Germany and my uncle had the originals in German (the 1995 THX release). So that was the first time I saw the original versions of ESB and ROTJ and he let me borrow the tapes and I would play the SE and the original on two VCRs at once switching between them and comparing the two versions. And I was horror struck when I found out that some of those beautiful cool special effects shots in ESB that I'd admired so much and watched frame by frame, because I was amazed that they were able to do that back in the early 80s without computer graphics, had in fact been altered - I vividly remember that moment - it was Falcon's cloud city approach and all the matte lines and harsh edges were gone in the SE and I felt cheated, the effects in the version I had been watching until then weren't cool anymore because they actually did use computer graphics, so to me as a child of the 90s, there wasn't anything special about them. I guess that was the moment I became a purist; when I was 12 or 13. And I became interested in the subject and read a lot about it and in time I realized that the originals were superior in every way, not only the effects.
But at the time, I was a content purist, because I went to high school to a bigger town, where I managed to find the Czech VHS release of the originals, so since the SEs were also only on VHS, I had them in the same quality.
It wasn't really until HD came around that I became a discontent purist. My country was always a bit behind the times with technology, so we got our first DVD player around the time SW came out on DVD in 2004 and that was also the year I first went to England and I bought the SW DVDs there but along with them I also bought a used 1995 THX widescreen VHS set, and because we only had a CRT TV, I was perfectly happy with that for the time and then when I went to England again two years later I bought the GOUT and was pretty happy with that too.
But then in 2008 we got a new 19" monitor with HD resolution and I first downloaded the HDTV rips of SW and then finally there was no version of the OOT that could come close to that quality in my eyes and that's when I became very unhappy with the situation.