It is pointless to submit an issue for debate if you are only interested in hearing the opinions of others who agree with you. By submitting an issue to a public forum, you should be prepared for and willing to listen to all points of view. If you are not, then you are not really prepared to debate.
If you are allowed to moderate comments on Debate.org, you could completely prevent people with the opposite opinion from posting. This completely loses the purpose of the site and actually allowing a debate to take place. For a real debate to take place, people have to have the freedom to post their opinion, even if it is against what the asker personally thinks.