Protests are meant to be disruptive. It stops people in their steps, demands attention and force people to have to deal with them. Any kind of protest at any non-designated area is by definition disruptive. That’s why we have the Hong Lim Park, a dedicated place for public protest, a place where disruption can be tolerated.
With the internet we have now, we do have a lot of space to protest and voice out even if people claim we are being censored. These days I see more anti-PAP opinion then pro-PAP propaganda all year round. We all actually spend time reading these and discuss issues offline and we get their point. We really do not have to go out to the streets for demonstration.
Sometimes we forget that the pro-govt also have a voice. If public protests are legal, they will not just sit and watch forever. Public demostrations will lead to conflict, breed resentment, destroy the social cohesion, and divert our attention from nation building, economic progress to petty disagreements.