Having the same issue with this extension that I have with the Porn/Malware blocker extension: it does nothing. When you first search in Google, it turns on SafeSearch automatically - however, you see a popup notification from Google that says "SafeSearch is turned on. Explicit results willbe filtered." and next to this notification is an option to disable SafeSearch, which works. So even though Google now defaults to SafeSearch, it can be disabled without even opening add ons manager.

Update: I should clarify, this problem is only relevant for image search. It appears that for website and video searches its not possible to disable SafeSearch from within Google, however when you go to the image search results, the option is presented to you. Nonetheless, much like other have commented, you can still disable the plugin through addons manager anyway, so it really amounts to no protection at all.

Had to disable because the extension was overriding amazon links to its affiliate link and which redirected to an error page. Hijacking links for profit is not what I am looking for in an extension.