Finding a live dinosaur does not in any way disprove evolution. It would simply mean that some very few dinosaurs lived through the extinction event. These Christians really need to take a class in evolution. That way they would know what they need to disprove.
Unfortunately, humans are very, very good at confirmation bias. Selective memory and biased interpretation can turn nearly any fact into any opinion in a very few steps. It is difficult to teach ideas to ideologues of any stripe (Christian, Atheist, Republican, NPR listener) because of this fact. And before you nod with an arrogant smirk, you do it. I do it. We all do it unless we're trying very, *very* hard not to... and then we still usually do it. It's ingrained. It insidious and subconscious and we really can't avoid it. The best we can do is be on our guard.
"'Tis true, 'tis pity, and pity 'tis 'tis true." -- Poloniouius, in Willie the Shake's _Hamlet, Prince of Darkness_