Using justifications are powerful in that they:

$1$ point

Enable you to refuse the other$$s solution, not because $$you do not like it$($although that may be the case$),$ but because there is a legitimate reason to take it off the table.

Provide $$destabilizing arguments$$ that allow you to score psychological points over the adversary and sap their energy to resist your solution.

Help you maintain the relationship with the other side: $$I$$m not saying no$,$ but facts X and Y justify that we do not include this option in the deal$.$

Provide a springboard for exploring other, legitimately anchored solutions.