Cannot delete user that has a Human Activity assigned

We have an application where we use BPT to assign tasks (Human activities) to users. This works fine, however I can't delete a user once a human activity has been assigned to them. This is regardless of whether the task has been completed and the process is done or terminated. This is because {Activity}.[UserId] has it's delete rule set to protect

It seems a bit extreme to delete the entire process(es). Any ideas on the best way clear the UserId from the activity so I can delete a user?

HI Herre,

You need to assign this activity to other user and than delete this user.if you do not want delete activity.