UGH How do I stop fiance countering pre-nup argument with the same statement every time?

We've been engaged for about 5 months, and he earns about 5x what I do, and has a few properties including owning his house and he wants a pre-nup to protect such, and I said to him that asking for a pre-nup means you are just prepared for the marriage to fail and he always comes back with "if you aren't intending to leave then there should be no problem with you signing it" how do I counter this, which I think is non-valid anyway because if it does end I should get something.

UGH How do I stop fiance countering pre-nup argument with the same statement every time?
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