This activity has already be answered by one (or several) users and cannot be deleted

As the subject says, I am struggling with "This activity has already be answered by one (or several) users and cannot be deleted". I realize I could delete the user(s) who have done the activity, but am hoping there's a better/easier way. Perhaps even hiding the content instead of deleting it? I will come back to edit this post if I find my own solution.