Their interpretation of the hadith is wrong, as the burden of sin can not be transferred and it is actually unjust to punish someone for the deeds of another.
لا تكسب كل نفس إلا عليها ولا تزر وازرة وزر أخرى
Every soul earns not [blame] except against itself, and no bearer of burdens will bear the burden of another.
— Quran 6:164
What the hadith actually ...
If there is no possible way of doing so, then read all those prayers afterwards. Then by the will of ALLAH , it will be accepted. I understand, i had the same difficultly aswell. If anyone understands, it is 100% ALLAH.
You have to understand that the real question you're asking is:
Why does Allah allow evil to happen?
From a technical view Satan is just a medium for that. If that's understandable then this question is already answered.
Specifically about this question:
God is just. Yet he has no guarantees that he will set justice in this life. His promise is for the next ...