In the Blacklist make it so you can block anyone, even characters that haven't been made yet, by simply inputting a universal name to block. For example, if you put ABC in your "Universal Blacklist" then anyone with ABC in their name (just like that, not everyone with those letters in general in their name, I.E. ABCjack = blocked and Abaca = not blocked) will be blocked by you. You could also be more specific to better not block innocents, but good luck to the advertiser to try getting around that
In the unlikely event it DOES block an innocent (which it shouldn't if you only use it for this purpose as blocking them too means they are probably helping them and/or shouldn't have a name like that anyway) simply add them to your Friend List if you wish to not have that innocent blocked too.