I could tell from all the people already dissing Arc before it was released that whatever I released was going to be attacked on any possible pretense. So, like someone bracing himself to be hit, that was what I was thinking about as I was about to release it: what are people going to seize upon as a way of attacking it? Which meant that was what much of the initial announcement ended up being about.
It was a pretty odd situation to be in. If I'd been releasing Arc into a neutral environment, I probably would have said what I wrote in http://paulgraham.com/core.html. But maybe it's just as well I gave all the flames something to expend themselves on before talking about subtler questions.