As usual, the government wasn't looking at the big picture. They
just wanted to benefit from the pride and prestige that hosting
such a prominent meeting would bring, and felt that they could deal
with the potential for disorder with the same high-handed tactics
that have been successful in keeping their citizenry in line for
years (i.e., blanket bans).
In a way, those tactics are working: there have thankfully been no
violent protests or demonstrations thus far. But Singapore's
reputation in the international community has been damaged.