ويجعل المنكر كغير المنكر إذا كان معه ما إن تأمله ارتدع عن إنكاره
A denier is treated as a non-denier when evidence is available which, if reflected upon, would turn them away from denial.
Under the ordinary rule, a denier calls for emphasis. But if adequate signs and arguments are plainly available, the speaker may use an unemphasized assertion, treating the listener as one who should not persist in denial.
This does not assert that the listener has already changed their mind. Instead, the speaker appeals to accessible evidence that ought to dissolve the resistance. The rhetorical form reflects that evaluative stance.