This is a great example of why both sides of a story are needed. From DEF CON's perspective, assuming this is all true, there's nothing unreasonable here.
It sounds like Dmitry was a subcontractor of Entropic and producing a screen asking for money after their contract had been terminated (for good-sounding reasons) was bad form. I'm not commenting on the legalities (I don't know anything about contract law) and I don't necessarily take either side's account at face value, but this response doesn't sound unreasonable to me.