do shi-gatai 度し難い Hard to persuade-and-make-understand.
Even if you tried to persuade them, you don't think they'd understand.
They're irredeemable. Beyond salvation.
do suru 度する
To persuade someone to understand.
To make them see the truth, the logic, to make them see the light.
To redeem. To save. (from saido 済度, "salvation," Buddhist term.)