When Monica activates David's imprinting protocol, he ceases to be just a "supertoy" and is now able to love like a real human being. The real heartwarming part? David calling Monica "mom" for the first time.
The people at the Flesh Fair oddly enough, David (not really knowing any better on top of being scared) cries out that he's actually a real boy. His very believable cries of panic move the audience so much that they all step up to defend him from Lord Johnson Johnson and riot.