I think not being able to view the website if you have ad-block on drives away traffic.
But here is an example i made on photoshop.
The way it works it is. If ad-block was ON. The ads would turn into a normal jpg photo. The same size and shape of the ad. And be shown at the the same location of the ad.
The jpg photos would have your message to the people.
This way the user would be able to see where exactly the ads are. Instead of blocking access to the website or having a big message at the top.
And when the user clicks on the jpg photo. You could create a xenforo page. Explaining why ads are important to the site and blah blah blah.. pretty much trying to beg them to turn it off.
Ive seen some websites do this. And it caught my attention and i turned it off for them.