'Grant' is one of a number of verbs that can appear in two kinds of structures:
The king granted freedom to the slaves.
The king granted the slaves their freedom.
In the first sentence, the slaves are the object of a preposition 'to', while in the second, both 'the slaves' and 'freedom' are just noun phrases, without accompanying prepositions. English has a lot of verbs like this:
I threw the ball to the receiver.
I threw the receiver the ball.
She gave the child a book.
She gave a book to the child.
…and so on. You could google 'double object construction' if you'd like to learn more.
So far, you sound like you ought to be right; there's a structure with a preposition, but another one without one, so the preposition shouldn't be required.
For many English speakers, though, when you have two objects, with no prepositions, the first object can't be questioned or relativized, as you're doing in your example. So a lot of speakers (including me) don't like examples like:
the child he granted freedom
the receiver I threw the ball
the child she gave the book
I think this is supposed to be a point of variation among English speakers, though. So I guess one question is how you and your friend feel about these kinds of examples in general. If you consistently disagree about them, it's not that one of you is right and the other is wrong; you just don't have identical grammars, which is very common, especially in a language as large as English.