Let me add to my first answer. If you need to develop an external service, which you have to for up to date lists.
As a software dev let me tell you. Dont forget the legal nightmare you will have to manage.
For example here in germany. Using google fonts, which every does, but not mentioned it? Sued.
Using local storage (cookies) to store application state, which every one does, but not mentioned it? Sued.
Dont mentioned contact info with real name and valid address? Sued. If you add the info think about the ppl who gets shamed on your website, they now know how they can meet you in rl.
Someone used the text input for behaviour description to fill it with racism for all users to see? Sued.
Do you use an account feature, but dont think about the laws for securing user data? Sued.
Do you want to earn some money with adds to help with server cost? I hope you have registered a business and have your taxes in order - else sued.
If you dont develop an external service and implement it as an addon which will try to sync the lists between players you meet in the world you have problems, too.
First the lists will never be up to date. A lot of people need to use it and meet one another for the addon to sync lists.
Now think about someone who intentionally fills his list with racist stuff. His list will be propagated to other players and they will forward it further. Great now you have an addon which spams others with racism and every one who uses it gets banned.
Just dont dude. Report them and move on.
Edit: Using blizzards IP for a naming and shaming website - sued, like boss level sued.
