[Idiom] What does "that will to be rightful must be reasonable" mean?

[NewHope]

Does it mean "if that will wants to be rightful, it (that will) must be reasonable?"

Context:
All, too, will bear in mind this sacred principle, that though the will of the majority is in all cases to prevail, that will to be rightful must be reasonable; that the minority possess their equal rights, which equal law must protect, and to violate would be oppression. Let us, then, fellow-citizens, unite with one heart and one mind.

 

[SoothingDave]

I see it as "if the will (of the majority) is to be considered rightful, then it must be reasonable."

 

[NewHope]

I see it as "if the will (of the majority) is to be considered rightful, then it must be reasonable."

Thanks