The issue not so much the extensions scraping the individual user's own data (or data about them) but scraping data about advertisers and about other users.
Facebook is harmed through resource consumption by the scraping, the infringement of any copyrights they hold on what's scraped, and potentially harmed in their relationship with their advertising customers and their users.
How bad Facebook's own practices are is irrelevant to the issue of what these extension makers have done. Dirtbags have rights too.
With as little respect I have for Facebook, and how reluctant I'd even be to defend them, your last sentence, "Dirtbags have rights too." is an attitude I think we all should stand to live up to these days.
I agree with your last statement that dirtbags deserve rights too; however, companies should not have rights on par with civilian rights at all. Hell, I'd like to write up a TOS they implicitly sign by taking on my business. ...while we're on the subject of normativity, anyway! :)
Facebook is harmed through resource consumption by the scraping, the infringement of any copyrights they hold on what's scraped, and potentially harmed in their relationship with their advertising customers and their users.
How bad Facebook's own practices are is irrelevant to the issue of what these extension makers have done. Dirtbags have rights too.