C4-6 are a reduplication, not unnatural indeed, but pro tanto tautological.
“Yes, but not for motion without the ‘pro,’” objected de Spain.
You will never be happy if the pro and the con distress you alike.
Don't you see that with Sawyer on pro there's a big hole in the line?
The Catholics raised the banner "Pro religione et libertate!"
When we parted, did you go to ...