Maybe some think silence is a sign of approval, and they refuse to approve?
I'd enjoy a spicy debate about almost whatever under the sun, as long as it is carried out in a respectful and civilized manner. Unfortunately, years have proved that to be something next to impossible - it always gets ugly or off track.
One of the reasons might be the nature of a web-debate: One writer bases his/her opinions on years of studies/professional experience/education, one on religious or political things and the third one on what he/she heard on the subway this morning.
They all feel they have a good case, but the starting points are too far apart. Internets curse "every opinion has equal weight" makes it really hard to have a discussion that makes any sense for longer than half a dozen posts.