Yes, screening should be permitted. SARS is a very dangerous disease and is easily spread. It is important to public health to keep certain diseases out of certain countries, and an airport screening is a great way to do that. People with early stages of SARS might not even realize they have it yet, so this screening could be healthy for them as well.
Diseases on planes, in addition to terrorists, can threaten world security and peace. Who is to say a person, intentionally infected with a deadly disease, can't fly to some peaceful nation to start an epidemic? SARS can be unintentionally spread by people traveling from one part of the world to another, so why not take the extra step to screen for it? When people enter the United States for immigration purposes, they are given a basic health screening. Since travelers are already subjected to invasive scans at airports, health screenings should be added anyway.