If you goto Options>Settings>Hide Thing> Show Memphis Posts Menu check this
A menu on the left side should appear called mDocs Posts.
Select all the posts in that menu.
First goto Settings>Default article Settings> uncheck Allow people to post comments on new articles
Then Goto the mDocs Posts Sidebar Menu
Goto the drop down menu that has the name Bulk Actions
Choose Edit
Then Apply
Find the dropdown that says Comments
Choose Do not allow
Update
Now all post in the past and in the future will not have comments
THANKS!
That is what I was looking for :
Settings>Default article Settings> uncheck Allow people to post comments on new articles
It took me quite some time to find that this checkbox was under Settings/Discussion.
BR