How to prevent user from deleting parent folder

I'm trying to figure out a way to create a folder for a group of users in the Reporting Services Home folder so they can have their own isolated container. The problem is that as a member of that group, i'm able to delete the parent folder!

Here's my setup:

Site Settings:
user_group = System User

Home Folder:
user_group = Browser

Group Folder:
user_group = All permissions