"Actually, the song goes to E7 because it's the dominant chord in the relative minor."

Well, yes, because the next chord is A minor. On the circle of fifths, they are next to each other--E and A--and any notes next to each other on the circle are harmonically related. So if you have CADG and want to vary it up, you find another harmonically related note to precede the A. E works because V resolves to I very nicely but E can't be minor because the A is already minor. You're just substituting the E as an alternate I.

"There is a D in the melody at that point which isn't in the I. I know this because I have been fooling with the chords to that song for the last 40 years;-)"

D is ii. What else can it be in the C scale?

"If it is dumbing down, it is dumbing down that was inspired by Phillip Glass, Steve Reich, Miles Davis, Stevie Wonder,"

Minimalism is a Zen concept of less is more. It has nothing to do with stripping things down to make them simple for simple-minded people any more than haiku is meant to be poetry for the mentally retarded. It's taking out the fluff and leaving the essence. Minimalist music and film are incredibly rich and nuanced. A film as "Samsara" is minimalist but is audially and visually far richer than the average Hollywood blockbuster. Below is a trailer:

Samsara trailer

"If it's "degeneration", remember that that's what they called Stravinsky."

When you can prove to me that Katy Perry or Eminem are in any way on the same level as Stravinsky I'll be happy to admit defeat. Well, I won't be happy--I'll be shocked. While you're at it, please prove to me that Miles Davis and Stevie Wonder are minimalists.