"When in Rome, do as the Romans do" - St Ambrose, 387A.D.
IMF, World Bank, activists and whatever, they are free to do what they want to do so long as it is done within the confines of the laws of our country. Remember, it is the right of the leaders of our country to do what we voted them to do, keep the peace. They as guests to our country need to observe our ways, and many a times, it is written in our laws.
If these activists feel that they have an important role to play, then observe our laws, and do it the way we have been doing it, discuss constructively and be prepared to protest in our way. But if they cannot do it this way, then do the right thing, don't come, else be prepared to get spanked real good. I reckon most Singaporeas will not welcome them either, I know I won't. Besides, there are always other opportunities to speak up elsewhere, in their own way, in countries where the law is more liberal to their methods.
For these people, if they do not like it, they should feel free to speak up, and Singaporeans should not be too petty or feel upset. After all, it is in their nature of our more liberal friends from the west to speak out at things that they don't agree with, which has it's benefits, but more importantly in this context, not always right. For every one person who criticises Singapore for being too rigid with this matter, there are probably 10,000 people or more from their own countries who probably don't give a hoot about it, and probably 1,000 or more other people from their own countries who rather have it the way it is handled now in Singapore, if they face a similar situation in their own country. Certain parallels can be made with the Michael Fay incident, the background it it may be very different, but the proportion of views held will be the similar.
For the rest of you, give it a rest.