Sorry to pile on but, the google sign on also turned me away. I have a google account and usually use it to sign up for sites I'm interested in but when it's used to gate content that could be accessible without a login I just feel like my data is being harvested.
If you really want to keep the login then maybe a message like we won't spam email you unless asked and only want your to log in to protect against bots would help.
If you really want to keep the login then maybe a message like we won't spam email you unless asked and only want your to log in to protect against bots would help.