No guilt
I have no compunction on using adblockers on sites which do not offer me an alternative way of avoiding the ads. I would rather pay real money (in small amounts) for content I wish to view rather than have my enjoyment of that content spoiled by ads.
I don't know how much sites get for just displaying ads - certainly from me they never get click-thru payments - so allowing me to make a small donation for a period of ad-less viewing would probably put them ahead of the game.