Google LOG IN request denied - what to do next?

Hi there,
I recently applied for Google log in feature for my gambling affiliate website with only 1 single scope - email. But my request was denied because my website promotes gambling. I've seen many many similar websites have Google LOG IN implemented in their websites. How did Google approved their websites and deny mine. I've implemented already succesfully Facebook LOG IN.
I received that message:

Hi,

Thank you for your patience. It looks like your application is not compliant with the following policy under the Brand Resource Center: Rules for Proper Usage. Therefore, we are unable to approve your request. Don’t display a Google Brand Feature on any website that contains or displays adult content,promotes gambling, involves the sale of tobacco or alcohol to persons under twenty-one years of age, or otherwise violates applicable law. For more information, please refer to the following resources: OAuth App Verification Help Center Google APIs Terms of Service Google API Services User Data Policy Thank you for your patience. If you have any questions, please reply directly to this email.

do people need to log in?
cant you let them register?

yes, they need because of the forum. it's not the site in my signature