Clear explanation on why Barney is Satan

1) Start with the given:
CUTE PURPLE DINOSAUR

2) Change all the U's to V's ( which is proper Latin anyway):
CVTE PVRPLE DINOSAVR

3) Extract all the Roman Numerals:
C V V L D I V

4) Convert into Arabic values:
100 5 5 50 500 1 5

5) Add up all the numbers:
666

Thus, Barney is Satan.