There is a big difference between fatigue and tiredness (sleepiness). Fatigue is longterm and is health related whereas tiredness may only last for one duty - granted the consequences may be the same. For whatever reason if you are not fit don't fly; that is your responsibility.
Tiredness is also often self induced or at least under an individual's control. It is up to everyone to take personal responsibility for their rest; you should know what hours and lifestyle the job entailed before you started; if you are not suited you shouldn't have become a commercial pilot.
I'm not belittling fatigue, it is a serious issue and should be tackled as such but I've seen too many use it as a scapegoat for their own irresponsible behaviour. If fatigue is not believed it will not be addressed by the companies or the industry. Comments such as the one in the lead article 'Some airlines are fatiguing pilots by forcing them to work for 20 hours without an adequate break' is not correct and consequently will deminish this serious safety issue.