I was actually there. The backlash against digital art usually came from:
people who were otherwise already elittist towards one or two painting styles and media,
art gallery regulars (they can't sell JPEGs or PSDs),
poor people as back then graphics tablets were way more expensive and alternatives to Wacom also worse (the patents for their battery-free pens haven't expired yet), thus it was cheaper to buy paint and/or markers.
I mean in all fairness, the difference is way more significant. Going from drawing to drawing on a screen is a bit different from drawing to typing text and letting a computer actually do most the work for you.