First and foremost, I think it's important to note that it is not someone's right to post anything to Hubski. The first Amendment does not apply to a private network. That said, I started this site to give people a place to share ideas and opinions, and to discuss a breadth of topics.
There are types of content that I do not want to host. Early on we had some posts from /r/beatingwomen, and I informed the author that I wasn't keen on hosting that content. They were cool about it.
One of the reasons why this topic is so charged is because it is not possible to make a statement about what will not be permitted which will be universally understood, much less agreed upon. There will be grey area when it comes to blocking content.
The primary goal of Hubski is to provide a place for thoughtful exchanges. I feel comfortable blocking images of beating women, because I did not set out to create a place for them. Perhaps if I felt this type of speech was important and threatened, I might spend my time building a place for it. I don't fault anyone for doing it, and I strongly support their right to do so.
At this point in Hubski's development, I don't think it is necessary or very useful for me to attempt to create a laundry list of what is acceptable and what is not. Currently, if there is content that we have an issue with, we will deal with it, and perhaps use the experience to better define that grey area for everyone.
I can tell you that most people consider me a very open-minded person. I am not easily offended, and I don't think that 'offensiveness' is necessarily equivalent to 'unwanted'. It is not my goal to ensure that any particular user is not offended. Hubski will contain a certain amount of material that might be found offensive. My very basic litmus test is whether or not a reasonable person can find the content thought-provoking. If I would have a very hard time finding a person that would find the content thought-provoking, I won't have much qualm about removing it if is problematic.
Regarding the tone of comments, we are working on some functionality that addresses it. It is still a work in progress, and I'll save the discussion on that for when we roll it out.