What about a simple hack? Something along these lines:

function getFaculty($facultyType) {
	$type = str_replace('_', ' ', $facultyType);
	return DataObject::get( 'FacultyPage', "`FacultyType` = '$type'" );
} 

That code simply replaces all underscores with spaces. Therefore underscore is an alias for space.
In the template you would then write:

<% control Faculty(Associate_Professor) %>
      <p><a href="$Link">$Title</a></p>
<% end_control %> 

Note that I put an underscore instead of a space there. And that I wrote Faculty instead of getFaculty, since you usually skip the "get" in the Template and it still maps to to correct function.

that does the trick, thanks!