Enraged? Bull elephants can be enraged, not authors.
Knowing a lot of the self published authors on Amazon, I can't imagine any of them stamping around smashing crockery and writing to the Guardian. Stop sensationalising a couple of whingers who obviously have written crap books and will see their income drop from £5 a month to zero, making no difference at all to their standard of living.
I expect they will be 'devastated' as well after July. Note that Warsaw and Dresden in WW2 were 'devastated'; I'm not sure you can compare writers to that.
Keep things in perspective will you, otherwise you will be likened to the 'Daily Outrage'.