Ever since Frank Gehry unveiled his design for the reinvented Art Gallery of Ontario, the plans have been under attack from community groups and preservationists concerned about cost overruns and the detruction of the existing AGO. Gehry is not known as a fiery figure, but the piling on appears to have gotten his hackles up. He hotly disputes the notion, advanced by a prominent columnist, that his projects frequently come in massively over budget, inviting the writer to produce numbers to back up his claim. And as to the charge that his plans would wipe out a popular sculpture atrium added to the AGO in 1993, Gehry claims that his design will leave a large part of the atrium intact, and that the overall expansion will enhance the space.