In running an online think tank I have noticed that many people come and go who are only interested in attacking ideas or individuals in a combative way. This happens on Blogs, Internet Forums and many other online communication communities. Why does this happen?

Recently in an online think tank such a combative chap came to criticize many ideas. One of the ideas was a stationary bicycle, which could also charge the spacecraft, ISS or Lunar Colony battery systems. He indicated that this was an ridiculous idea and stated;