Good argument but I still don't agree with it completely. First of all lets separate devices into three categories - desktops, laptops and touchscreen.
For desktops CPU and RAM are largely irrelevant in such amount (temporary up to 25-50% CPU usage increase for one core, and up to 500-1000Mb of memory usage increase in worst case - for instance my FF never exceeds 1Gb overall with ABP and other stuff). I sometimes "fix" old PCs for relatives and even in worst cases ABP usage isn't a noticeable hit on performance.
For laptops resources are more relevant as well as battery life. I'll even agree with your point for this category, but still for now ABP hit is not that big as compared to ad noise.
For touchscreens resources are very important BUT! This is a very big "BUT". But the websites are almost unusable without adblock. I use iphone and ipad where there are no adblockers afaik. When I browse the web it is horrible (with a big H - Horrible) - everything is jumping, jiggling and wobbling for a long time during page load. One moment there is a text in some point and I try to scroll - and instantly there appears stupid facebook crap which I of course click. Same with multiple frames, banners, popups (I hope these devs will burn in hell). And additionally there weird motion gestures in-built into page, transparent overlays which are part of a nearest ad. The list goes on...
Basically on touchscreens web browsing experience is so horrible that I'm willing to trade adblocker for x2 increase in battery consumption (note that web browsing is not the only thing to do on a phone or tablet, so this is not a total x2 lifetime decrease).