That thread was full of knee jerk reactions and deficient in sound reasoning for a good while. I think Roman Shaposhnik had the best point when he noted that you could do something like Cilk (not exactly the same, but similar) as a library if C had closures, instead of as a new language supersetting C. It's not like block scoped functions are in any way new or unusual; even gcc has had downward funargs (which aren't enough to do GCD with, FWIW) for years.

The thing is, Objective C is the main way to develop Cocoa applications. Blocks, garbage collection, and a number of other features that have been roundly whined about are ways of increasing the expressivity of the language so that it is more comfortable to write applications in. One can argue that C is a miserable applications development language (and I think you'd be right) but unfortunately we have relatively few other options. Apple used to have a Java-Cocoa bridge that has been deprecated for some time because nobody cared.

I will never understand why people don't give new (ahem) ideas the time of day. There's no reason why C has to be set in stone.

Blocks in C have lead to a great simplification of my own code. A lot less jumping from method to method. There is no way that these are a bad thing.