The tone is like that because people have been saying that Telegram's protocol was constructed seemingly arbitrarily and includes outdated and mostly-unstudied constructs. No serious cryptographer would build a protocol like that, and many well-known cryptographers have pointed that out.
The Telegram team has been hostile to legitimate criticism, and has hosted cracking "contests" as if that in any way demonstrates the security of their protocol. When you roll your own protocol from practically unused primitives, commit most sins in the crypto book, dodge criticism, store your users' messages, and refuse to open-source the server-side code, you deserve that tone.
When news comes around about Telegram it typically includes the criticism of their team being hostile. I just haven't seen it though. Instead I've seen their team respond to posts with gratitude for the critique and disclosure. I think this is where I get perplexed on this topic. Though maybe I just missed a particularly hostile event.
It's just rather dodgy all the criticism. What other secure chat system of late provides the server code? Only Pond comes to mind. What other chat system provides an OSS client, Only Pond TextSecure and Telegram.
Cracking contests are either absurd or just asking for people to ridicule you. So I understand part of the animosity.
The Telegram team has been hostile to legitimate criticism, and has hosted cracking "contests" as if that in any way demonstrates the security of their protocol. When you roll your own protocol from practically unused primitives, commit most sins in the crypto book, dodge criticism, store your users' messages, and refuse to open-source the server-side code, you deserve that tone.