If they were using something federated and secure like XMPP+OTR, sure, but Telegram is as easily moderated as any other centralised solution (they might as well be operating on an FB Profile + FB Group Chat).

If the DOD/NSA/CIA/WTV wanted to shut this down (which they likely don't as this probably serves as a nice stream of data) all they need to do is shut-down Telegram's US servers, which would likely cripple the entire company financially.