It sounds to me like they were mad at Dmitry for including an "easter egg" in their badge firmware that solicited donations to a Bitcoin address.
It probably shouldn't have had the Bitcoin address, but it doesn't sound like that would have been treated much differently.
But it's objectively an easter egg. Why the scare quotes?
And unpaid programmers doing cheeky things with code because they want to is the heart of DEFCON.
I can see where DEFCON is coming from with the calls they made here. But it’s a mistake to treat Dimitri as if he were a vendor. He's not.