Contrast rebellion refers to W3C's Web Content Accessibility Guidelines, which specify a contrast ratio of at least 4.5. Just for fun, I plugged in the numbers, the site has a contrast ratio of about 4.9.
I'll take a look when I've got a few more moments to see where various of the W3C's recommendation levels fall on my own assessment of readability.
Speaking as a 40-something with decent vision, the site isn't impossible to read, but it's most definitely annoying. For someone with compromised or old eyes, it would be much worse.
W3C: http://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contr...