Mass removing security groups


I am trying to mass remove security groups from all selected contacts. I go to contacts, select all records and then click on “remove” next to “secuiry groups: Mass assign” option, however, first it asks, if I am sure if I want to delete 2 records (I am not clicking on Delete) and then when I choose ok, it says “please choose a group and try again”, even though my goal is to remove the group, not to choose a new one.

I wonder whats the best alternative to this?