It is possible that you want this default only because neonazis haven't heard of steemit.com yet. I come from the seedy underbelly of the internet and know that the only reason we don't have problems with content right now is because of how small we are, and fully expect people to spam all sorts of terrible crap on every article posted soon.
It is my personal opinion that we should give an author 100% control over what gets displayed underneath their words, lest they go and publish their words somewhere else (almost every other blogging platform on the planet gives an author this control).
If our decision is wrong, then people will flock to busy.org (or some other site that doesn't lets authors moderate) instead, won't they?
It's a design that makes sense - just worried about the points, similar to what @pfunk has brought up.
I'll take your word for it, I can imagine how bad it can get :)