> Why stop there?
Because we want to, and we can. I don't get how HN consistently fails to understand the actual social and political process by which regulations are made. I constantly see this argument which effectively boils down to "if you ban a thing, you will also need to ban everything else, which is absurd, so you shouldn't ban anything". But in real life we can choose what we ban. Everything is a trade-off; we can choose to ban something if the harm it creates is considered to outweigh its benefit to society.
It is open to society to decide that Telegram is more proximate to the harm being caused, and less otherwise socially useful, than an ISP, and on that basis punish the former but not the latter. (It is also reasonable to argue that Telegram is not sufficiently proximate to the harm and that it is sufficiently socially useful that it should be allowed to operate, and honestly I sympathise with that argument more. But my point is that it is a matter of weighing social harm vs benefit and not just a technical analysis of "where the bits go".)
If you get caught driving a getaway car for an armed robber, you are going to jail. Arguing "ah, but by that logic you'll also have to jail the guy who sold the robber his breakfast" isn't going to cut it, and rightly so.