Why does Dimsdale say Hester is better off to have the public know of her sin than to keep it hidden?

Dimmesdale remarks that Pearl embodies "the freedom of a broken law." When Pearl sees the two men, she hurls one of her burrs at Dimmesdale, who recoils in fear. Pearl then shouts to her mother that they should leave, or the "Black Man" who has already gotten hold of Dimmesdale will catch them. If the scandal is made public, Hester may not have to suffer what she is going through and Pearl might be controlled.