They're perfectly within their rights to do so. And I can't speak for anyone else, but my choice will almost always be, "I don't want to look at your site that badly."
"But! Moneys!" scream the website owners. "Hosting is expensive!" etc. Well, yes. I understand that. But you know what? I don't care.
Sometime during (or leading up to) the dot-com boom I remember seeing an ad for some corporation trying to market to middle managers, which had graphic design like a merchant bank and the header, "Finally, the web is good for more than UFO theories and pictures of cats."
My reaction then is the same as my reaction now: FUCK. YOU.
UFO theories and pictures of cats is what I want from the internet. Personal blogs, dorky little vines, silly memes? That's what the web is good for. The world needs another stream of commerce like I need another hole in my head. People making connections? That's what the world needs.
So people not being able to make money on the internet? That's all to the good. I want money out of the internet as much as possible, the same way I want it out of roleplaying games and conventions and universities and libraries and public TV and almost every other thing really worth doing. The relentless drive to prioritize short-term profit over doing the core thing that you're about has destroyed everything it ever touched.
The current crop of websites flailing around trying to block the ad-blockers may be a harbinger of the collapse of "Big Website," which would mean a lot of potentially-good content might be lost. On the other hand, it also means that a lot of clickbait garbage will also be lost, and I can live with that. I was perfectly content with grunky mostly-text webpages and very, very personal blogs. I have absolutely no problem with the internet being the realm of the hobbyist, now and forever.