Hearing Ding Dong talk about this again, and through my own personal experiences, I think I have a better idea of what actually conspired.
When Ding Dong was shown the Dream Daddy build by Matt, he obviously had some grievances with it, and after seeing how miserable it was making a lot of the employees working at Game Grumps, he decided to say something in an attempt to help after some urging from both Julian and some of the employees.
This is when the employees used Ding Dong as a guinea pig, allowing him to take the first step and test the waters before they spoke out as well. When they saw what happened with him getting doxed and blacklisted from the industry, the employees backed down. At best they would get fired, at worst they would never be able to get a career again.
It sucks, but when push came to shove, the employees chose their jobs over their friend. I know Ding Dong said there is a recording of him explaining everything, but here's to hoping we never actually hear it.
As for Matt, it seems like he cares more about his image than Ding Dong. But if he truly wants to be friends or make it up to him, be an adult, sit down in person, and have a conversation. Will it be awkward? Of fucking course. But after everything that has happened Ding Dong is still trying to make an effort to be friends, either reciprocate it or don't.
And for the members of Game Grumps who blacklisted Ding Dong. Fuck you. How fucking petty do you have to be to ruin someone's career because they spoke negatively about your visual novel game? Eat shit.