Am I the only one who feels like it isn't the responsibility of backbone ISPs to filter traffic like this? In the case of a DDoS situation I could get behind it, but in this case I feel as though it's not Cogent's problem if I want to use telnet from a device on Charter's network to a Vultr VPS, even if it may be ill-advised.

(Of course, the article only speculates that this traffic filtering is what's going on; there isn't any hard proof, but it feels plausible to me.)