No, and I hate it when websites make it practically impossible (if not blocking those nasty scripts) to use them. Running a bunch of websites I understand that it's not free or even cheap, but if your solution is to plaster your site with flashing images and even worse, autoplaying videos with sounds, you can just go die in a fire for all I care.
No, it would be quite hypocritical since I am an adblock user myself.
I've been to a few forums that have a dismissable notification requesting that I turn it off, but I can close it and continue accessing the site. That's fine.
On the other hand, I've been to a few forums that wont allow me to login unless I turn off Adblock. Those ones I just delete from my bookmarks and stop visiting all together.
No, I do not. If they would like to keep it on it won't block them from accessing the site or interfere. On my forum there is an option to buy a premium membership to support the forum without ads.
Nope. I use AdBlock+ myself, so making others turn it off would be pretty stupid.
Only time I ever really had to turn it off was on Bulbagarden's forums in an RP staff board because ad blockers weren't letting myself or other staff post in a thread that had "Advertising" in the title. It was a pretty funny scenario, actually. They don't really have any ads on their forum though, at least none that I've seen, so I don't really mind having it off there. I'll probably turn it back on once we're finished with that thread.