The reasons for the removal are actually more sound than you'd think, at least for some of the removed adblockers. AdBlock Plus, for instance, used a security vulnerability to allow it to work without root access. A tool like AdAway, in the meantime, took a more 'wholesome' approach and edited the hosts file to block ads everywhere - in browsers and ad-supported applications.
The specific section Google claims is being violated:
It's no surprise that tools like either of these two would not stand up to scrutiny of a curated application store, but of course, this is all just a convenient way for the world's largest internet advertising company to boot tools that possibly affect their bottom line. I have no idea how popular these tools were to make any statements about how large this possible effect is, but let's not try to turn this into anything other than it is.
I used AdAway on my Galaxy SII and later on my Nexus 7 (both relegated to storage now that I have an 8X and Surface RT), for the simple reason that I refuse to have my mobile browsing experience - already not the most optimal on any mobile device - further bogged down by ads on websites. The fact that AdAway also blocked ads in applications was of no relevance to me since I buy all my applications.
Thanks to Android's open nature, though, the removal from the Play Store means absolutely nothing at all. Every Android device (aside from some carrier-locked ones, I suppose, but I've seen those here in The Netherlands) can easily sideload applications - including these adblockers - so effectively nothing has been lost. Diving into menus to find the allow-sideloading-switch may be a bit too daunting for less experienced users, though.
Question remains what this move will mean for adblocking extensions for Chrome. They've remained untouched during this recent move, but what's to say they won't get the same treatments in a few weeks of months? I'd guess the impact of desktop adblockers is much more substantial than that of mobile adblockers, so Google may indeed be pondering such a move.
As for adblocking in and of itself - I never had much of a problem with it, despite OSNews running (a very limited set of) ads. In the end, your computer is your own, and you, and only you, get to decide what gets stored in your RAM or what gets displayed on your screen. If you do not want ads on your computer, then you have the right to block them client-side.