Wow, this is written in a really weird tone, especially considering it's coming from an official Twitter representative. It doesn't feel clear at all what they want developers to do. Either way, it feels very hostile.
If nothing else, I think it’s advice developers should seriously consider heeding if they want to create value (and generate revenue) using the Twitter ecosystem.
Regarding whether the tone is “hostile” or the message represents “a kick in the teeth,” I think people need to keep some perspective: A hundred and how many million tweets a day?! That's a lot! If I were responsible for the big picture at Twitter, supporting your junior high science fair project Twitter client would not be at the top of my to-do list.
What are the support costs? I would think you publish the API and it's up to the client to manage it from there.
At this point, Twitter needs to realize that the ambiguity isn't helping their PR, its the reason they have a PR problem in the first place.
EDIT: Minor grammatical correction.