But you already don't stop your ISP from interfering with your traffic in transit. So why is it a big deal if you continue to not do it? Or is seeing a few ads more important to you than, say, all of your email?
But, now they've seen their ISP tampering those people might switch on encryption for their email, and everything else.
For what it's worth I was grumpy in those situations too. I wrote polite letters. Where possible I opted out.
But your point - this kind of this happens all the time, and has been going on for years, and noone is doing anything to stop it even though it's wrong - is taken.