Even with Google's volume you have to take the 0.25% of claimed occurrences, then take the percentage of people who will be offended, then take the small percentage of people who will notice/know they can report it, then take the small percentage of people who actually bother.
And even if there won't be an organized effort to game the system it serves to the lowest common denominator of 'not offensive'. If I type "How to know if I'm t" and it autofills 'ransgender' that is fine by me, but some people will consider that offensive (don't ask me why) and report it. Or take for example unwanted pregancy, you can bet that if one searches for unwanted pregnancy and Google puts up a neutral snippet from Planned Parenthood people will report it.
It's one of the reasons I switched to ddg.
The SPLC is free to list whomever they want, but using their list to rank sites in Google search is very problematic.
[0] - https://www.splcenter.org/20161025/journalists-manual-field-...