I disagree that it is stealing because I never agreed (or wanted) to participate in this program. The site owner did.

I'm under no obligation (moral or otherwise) to make honest contributions. If we wanted to continue with your analogy, it'll be like being forced into a taxi, then driven one meter, then forced to pay a large fee because the landlord doesn't want me to walk on his lawn. I didn't choose to ride the taxi. The landlord did (ignoring saner options).

If google wants a revenue from their service, they should consider charging site owners.

If google wants to train their NNs, they'll have to pay people to classify data for them.

If google doesn't want to do either, and doesn't want people like me contributing to their system, don't let site owners allow us to use their site.

Otherwise, I think google should shutdown the service.