I don't think Adblock is really any worse than fast-forwarding past ads on my PVR (especially having never once clicked on an ad on the internet).

But an ISP blocking ads is very dodgy... An ISP tampering with web pages at all is wrong - I think an their job is to deliver only, and exactly what the web server gives them to the person who requested it, who is then free to choose what part of the page they see. All the more reason for more web sites to use SSL/TLS.