Answer:
either-or fallacy
Explanation:
In the either or fallacy a situation is presented as the only alternative of another situation. But in fact there are other alternatives of a situation.
Here, according to Marty unless people get rid of guns they will have to face the same situation of gun violence that people faced in Kentucky, Arkansas, and Colorado. He has not considered what might happen if the guns are still present. There are countries where the existance of guns and violence is not related.
Hence, Marty is using the either-or fallacy.