But you have no cause to assume that a person holding that position is being false. Perhaps you might be thinking that anyone holding a position of opposition to evolution on non-religious grounds is impossible. You have no warrant for that stance, it would just be your subjective opinion. (And then your treading into the no-true-Scotsman fallacy territory) The only other possibility that might work for you would be you think belief in Divine Creation and evolution are actually mutually exclusive, but then you're contradicting your prior statements.
But those who pretend to be doing this (concluding from non-religous reasons) never have any. It is the repetition of the claim with utterly inadequate backup which the gentlemen you have been discussing with are all to familiar with.