I think, given how many millions of minds it would have to affect and how much sanity increase it would require, it sounds a lot like 6 in practice. (Unless the approach is "Build a company big enough to buy Google, and then limit comments to people who are sane", in which case, 2.)
Or you could build a Youtube competitor that draws most users away from Youtube, which is between 0.5 and 1.
From Hacker News.
This made me laugh, but from the look of it, I'd say there is little work to do to make it serious. Personally, I'd try to shorten it so it is punchier and more memorable.