in a nutshell they're refusing to implement a blacklisting mechanism and being stubborn about it.
However, I do think there's an interesting debate on the opt-in/opt-out issue. People are saying that Google itself is an opt-out system, but the "right to be forgotten" seems like a real concern to me.
"Perhaps there should be a "black list" that prevents certain projects from being added. But I am not yet sure if we should develop this feature since motivation is not clear to me."