Grodd can control people’s minds. This apparently includes hero-types.

Get Grodd, er, ‘watching the colors’, and plop him down somewhere in the middle of a city.

As local hero-types come after him[which they will; he’s a known villain, after all], Grodd just offers to ’share the love’ or however you want to put it…presto, every hero-type in the area, as well as any normal people who didn’t get out of the way [such as, for example, law enforcement officers], are all tuned out from reality.

After this, the other plotters can do whatever they like, provided they’ve got equipment or abilities that will render them immune to Grodd’s control. [And I assume they would if they’re going to attempt this kind of stunt in the first place.]