What kind of fucked up site has 10+ iframes per page, let alone hundreds? And the example site he uses takes 530megs to load even without addons. I'm sensing the issue is somewhere other than Adblock Plus.
You could as well ask "What kind of fucked up add-on unconditionally injects minimum of 14K+ CSS rules per page? (assuming no iframe)".
The original point is that the approach is detrimental to Firefox the browser regardless of that stress test, and I can understand very well Firefox developers wanting to raise the issue [1], as the browser ends up taking the blame when resources are abused.
The like button is just one of many of Facebook's components which can be embedded into pages; another being the comment box which shows your name and display picture but cannot allow the hosting page to get at that information unauthorized.
FWIW, on a site I work for, we use a plain facebook like link without any personalisation because that's all we require, and we recognise that it respects our visitors' privacy more than the full-on iframe variant.