First, how can we be sure if they are Singaporeans? They could be new immigrants, tourists, PR holders, Malaysian temp workers. Why must Singaporeans always take the blame for bad public behaviors? I am a typical "Sinkie" but I never rush for empty seats on buses or MRT be it reserved ones or not.
Second, why do we have to argue about this in the first place? We should blame the PAP's population policy for causing the congestion! If there are only 3.5 million people there will always be enough seats for everyone who are tired.
Third, for those who blame picture-taker for being "coward", make sure you act what you preach next time. Good luck to you as you can encounter such unpleasant public acts almost everyday in Singapore. Are you going to intervene every time?