There is an excellent article posted here on TE about the "Cycling Myths":

http://www.teamestrogen.com/articles/articles_myth1.asp

Skip to the second article for "road tax" in particular. This will give you some idea of where motorists are coming from. There are some good facts to have when dealing with an irate motorists, if you can remember them. Not sure how much this applies in Singapore, but I'm sure some of it will help.