Earlier quoted context omitted.
How is it a moral issue? If it's immoral to block certain behavior on sites, then it's just as if not _more_ immoral for users to block ads in the first place. The usual argument is that sites with ads constitute an implicit agreement, etc. If users have the prerogative (regardless of moral ambiguity) to block content they don't like, sites have the same prerogative to block unsavory visitors as they see fit. To say…
No, I mean: I do not care about a website showing me an ad as plain . I have no issues with those ads. I have issues with ads running javascript, tracking me, and trying to abuse holes in my browser to install malware. And it is immoral to force people into running those ads.
An apt analogy would be a magazine on a table with a sign denoting the price. Without FuckAdBlock, the sign reads "Price: ___". Taking the magazine and not paying anything isn't immoral, it just shows you value yourself above others (nothing wrong with that). With FuckAdBlock, the sign now reads "Price: Your kidney". By taking the magazine and not paying, you're quite literally stealing, regardless of the price now on the sign.