I think it is safe to say that it can have an effect on a company's user experience.
Personally if I saw such a blocker I would have to really consider how much I wanted to use this site.
By blocking the content the site is putting up a "barrier to entry", something we normally strive to avoid in UX design.
From the company's perspective I understand that ad revenue may be a primary source of income and the fear is that if they don't do something to protect it, it will go away.
I can't speak for everyone, but I block ads due to their annoyance, performance robbing qualities, and quite frankly I just don't click on ads... they are rarely applicable to me (e.g. Trying to sell me dating site memberships... when I'm happily married).
If the site is depending on revenue from high ad impressions to stay afloat I would seriously consider working on a new business plan.
For anyone planning to sniff out ad blockers beware it is a cat and mouse game. Ad Block plus and similar add-ons may be somewhat easy to sniff out but that's only the top of the iceberg... Apple is enabling blocking on iOS Safari, the new Brave browser (on all major platforms) is designed to block ads by default, and DNS ad blocking has been a staple for many for years!
RE: Brave, Yeah it's a bit more complex than pure blocking... but ad blocking will continue to grow.
PS Although it might seem weird after the statements above, I'd be open to advertising (Internet, TV, Radio, Apps) if I could somehow create a profile so that the ads shown were at least interesting to me. E.g. On TV I've seen 1,000's of commercials for diapers, feminine higene products, denture cream/toothpaste, gym memberships, medication I've never needed, pickup trucks, etc. That I will NEVER buy. I'm sure just purely by numbers if I saw more Quiznos, Thai food, and various electronic device commercials I would be more likely to buy those items.