No, you've got it all backwards. The current situation is that SafeSearch exists and is on by default for any user who is not logged in; the children are safe from seeing boobs accidentally. Anybody searching on a machine that is not sufficiently locked down by the network admin can turn SafeSearch off and find whatever Google might have, without having to associate their Google login with their private searches. Anyone who doesn't want to see anything explicit can just leave SafeSearch turned on. There is no need for a change.

The proposed change means that no one can see anything Google decides is explicit without tying that search to Google account. You would have to login to see "explicit" results. No one would be able to privately search Google for something and have those results be ephemeral. Teens who don't know why that's a bad idea will just lie about their ages to get around the block and create a Google account that has way too much information about the explicit things they were curious about once, and may suffer consequences as a result. WON'T SOMEONE THINK OF THE CHILDREN?!?.

"I have nothing to hide" is a pretty poor reason to limit the freedoms of others.