This is one of the perennial problems that the dog groups face - the fact that whether or not they sterilise, the dogs still get rounded up. It really is a disincentive to sterilise - and it means that less dogs will get sterilised overall. If the idea is to make Singapore 'safer' than sterilisation should be encouraged.
I remember meeting someone at a conference a few years ago, and he mentioned that because rabies is rampant where he's from (someone had just gotten bitten), sterilisation of dogs was pursued aggressively and they saw fewer people get bitten, and better results healthwise. With less dogs, there will be less attacks, and less incidents obviously. Try and round the dogs up, and there will always be those that elude the traps and will just run around reproducing, meaning there will always be more dogs.