I don't get it. My ISP will sometimes make little notices appear in order to warn me of upcoming outages due to maintenance, etc. Is that illegal, too? I don't see the problem here.
And there's no date that I can see in the image. How do we know it's not 7 years old?
I know this is completely idiotic (really, it drives me nuts), but whether or not something is "wrong" depends on where you live. Hop over an invisible line, and POOF! Things become legal/illegal / right/wrong.
That's just the Canadian Telecommunications Act. Morality and the laws of the universe may differ elsewhere, apparently.
Aside from any legality there... if your communications are being subjected to injection, can you trust them? The **ONLY** answer is **NO**, unless you're insanely gullible. Compromised is compromised. This is a security issue, and not really very open to any kind of "interpretation". Either an attack vector is open or it isn't. That attack vector is either being exploited, or it isn't. There's no "gray" area here. It's all black and white. 1s and 0s. True and false.
The ISP here is exploiting an attack vector. Period.
(Keep in mind that there are no "MITM agreement" conditions set in contracts. e.g. "I agree to let my ISP exploit MITM attacks against me whenever they think it's good for me.")
But, aside from my pissy attitude towards all that, about the 7-year thing, check the video. It's a recent one from a security source with the same kind of MITM attack. He walks through it all and explains a truckload.
The video is rather long though. It's meant for computer geeks and not the general public, so it gets into SYN/ACK and all kinds of messy goodness.