The tool cylinder has to slide all the way down over the pin cylinder to depress the retention tab.
You have to use the smallest size that'll fit over the pin to depress the tab.
While inserting the tool gently push the wire into the connector then pull the wire and pin out of the back of the connector.

 

Sometimes it helps to push the pin into the terminal block from the back (wire) side first, then slide the tool over the pin to compress the tabs. Next, pull on the wire, and the pin should come out. Also, move the tool from side to side while pulling; this will help get the tabs into the hole they are supposed to pull through.

 

No matter what tool you have or your patience level or how many times you've done, they can be a pain...

 

Thanks for kind advices.
While riding harley almost for 30 years, I found myself still ignorant of this machine.
I will fix my jaw to complete this work for the sake of your advices.
If impossible, I will dissemble handle sides.