The problem is, short of banning encryption altogether, you cannot prevent people from communicating in near perfect secrecy. If a criminal (or neo-Nazi, or homophobic, or whatever scapegoat you want to use) organization wants to communicate secretly, they will have means of doing so. All it takes is single programmer to write the custom application, and a single AWS instance to relay the data.
By banning Telegram or enforcing government rules, you're only taking away privacy from ordinary folks, while doing effectively nothing to those who you're claiming to fight against.
...and no, this is not an argument for banning encryption. I hope that part is obvious.