Why is using the rails default_scope often recommend against?

Question

Everywhere on the internet people mention that using the rails default_scope is a bad idea, and the top hits for default_scope on stackoverflow are

Answer 1

Another reason to not use default_scope is when you're deleting an instance of a model that has a 1 to many relation with the default_scope model

Consider for example:

    class User < ActiveRecord::Base
      has_many :posts, dependent: :destroy
    end 

    class Post < ActiveRecord::Base
      default_scope { where(published: true) }
      belongs_to :user
    end

Calling user.destroy will delete all the posts that are published, but it won't delete posts that are unpublished. Hence the database will throw a foreign key violation because it contains records that reference the user you want to remove.