Half of Australians want to ban Muslim immigration, page-105

My point is that you miss out on people from countries which are more peaceful, you don't guarantee extremists won't get through anyway, and you lose a substantial amount of people who could immigrate and the benefits they would bring to our society (economy, culture, etc).

Also, note that due to how we have structured our intake, Muslim immigration is dropping anyway leaving others coming from these countries with skills we want. Check this out
http://www.theaustralian.com.au/new...n/news-story/6be73d718d50476f940e30281d885b99