From their main page:
(...) privacy-caring users can reduce or monitor data that is sent to Google (...)
From their dedicated Google connections page:
In general, we obviously try to minimize the connections to Google, but some services strictly rely on them and would just not work without.
I mean, sure you can ask for sources, but maybe take a little less aggressive stance when the information is so readily available. This took me way more time to write than you would have used looking it up yourself.