They are complaining because what Digital Domain is proposing is exploitation.
Having students pay $100,000 to work on the films that DD will then profit from is the same as saying:
"Pay us $100,000+ and we will let you harvest our crops for us to sell and profit from"
"Pay us $100,000+ and we will let you build cheap electronics in our factory for us to sell and profit from"
"Pay us $100,000+ and we will let you sew gucci handbag knockoffs for us to sell and profit from"
etc.
I applaud DD's attempt to help students get valuable practical experience, but having the students pay for the privilege of doing so is disgraceful. There is enough exploitation in the industry as it is - think about how many enthusiastic young artists have burned out and quit the industry because they were treated like slave labor.
If DD is serious about nurturing new talent, they should open up a VFX school like Gnomon or Vancouver Film School and do it that way, then let the students enter the company as junior artists.
They need to take their current idea back to the drawing board.