There is no human that does not believe in another possibility no matter how much he may try to do so, especially in cases like this where the original premise is simply not solid.
If we were talking about something simple like basic mathmatics(2+2=4) or something generally accepted with proof/ability to reproduce results, sure. But I'm pretty sure it is willful ignorance here.
They simply believe in something to make themselves feel good or some other reason(usually society).