Well if i'm Gregory i say something like that, they are very angry so they might listen. You know one of those parents will come back to you. Anyways. His plan could be use the other guy to go after Maggie, she'll kill him in self defense then people will want change because she can no longer be in charge. It'll break the we don't kill rule.
I then see Gregory telling people they need change and he can bring it to them and tell parents how kids will be safe and no more attacks...blah blah blah.
If this happens surely even Gregory knows they wouldnt re elect him the leader... Not after all the shit he did in the past... Im actually surprised Gregory is still around after he went to Negan...