I'm looking to allow users to create a "blacklist" of certain tags on a site. My plan was to do this through adding a "Blacklisted Tags" field on the user entity, but I'm open to other solutions. If an item is tagged with a tag they've blacklisted, it won't appear in a view. Is there a way to do this using default views functionality? If not, what's the simplest way to achieve this?
I guess using the ER field on user profiles is the easiest way, it all depends on your requirements.
If you need users to interactively "mark" tags on tags pages or through some other places you could use Flag modules and let them flag tags to blacklist them by simply clicking on the "Blacklist" flag link.
Either way you can build Views that show only content that hasn't been tagged with those.
Add the Contextual filter for the Blacklisted ER field (Default value...) then under
More check the
Exclude. This way your list will not show any content that has blacklisted tags.
Of course, your Contextual needs to be configured properly but there are many answers here you can find with all the options listed.
Flags views take some more steps to configure but the logic is the same.