Guild Wars 2

Obviously guilds that are sending out blind invites are not guilds that I want to be a part of and no one is selling themselves by spamming me constantly with invites. Is there a way to block them? They’re starting to get to the point where they’re abusive.

Nope.
But in my experience, they only ninja invite people that are guildless. I had the same problem untill I spent a silver on making a solo guild and started representing it. Since then I never had any unwanted invite.