It's quite possible for someone to rationally think that an action / service / startup is bad for humanity in general. How this interplays with humility is some

It's quite possible for someone to rationally think that an action / service / startup is bad for humanity in general. How this interplays with humility is somewhat more subtle. People write what they believe. If you had written a blog post about twitter being a service that shouldn't exist (which you apparently thought), how open would you be to someone asking, "Who do you think you are to have an opinion?" He had clearly written out reasons for believing as he did. Agree or disagree with them, don't try to attack the person.