These results pretty much speak for themselves. Just think of it this way, compression works by finding patterns (like every byte is zero), and only storing the patterns. If the encrypted data has patterns, then the plain text could more easily be found.
It depends what you want to show, in this case I was showing the size difference between a file unencrypted and encrypted. An all-zeros file has nearly no randomness, so it compressed very well. Then I show that somehow the encryption process takes away this lack of randomness, and leaves a file almost incompressible. I'm really just increasing the scale to make it more 'dramatic'.
If I happened to be showing how compressed codecs like jpeg, mp3 or h264 weren't compressible, I would definitely pick something more like an actual text file.
