I am looking for the name for the logical fallacy that compares the best samples from one group with the worst samples from the second group and concludes that the first group is better than the second. Example (maybe a little vague): In a gun-related debate a picture is presented with two doctors who were recently accused of murder and a person with a gun (probably a marine) and the question is asked: "who is the real murderer?" The conclusion that one is supposed to draw is that based on this comparison of "the worst" of the doctors vs. "the best" of the gun users is that the whole group of gun-users is "good".
Informal fallacies have fuzzy boundaries. This seems to me to be a variation on "cherry picking," which is basing a general conclusion on a few carefully selected data points (which may not reflect the larger trends).
There is one example of this kind of thinking that still exists in too many places; it is called, Ethnocentrism.
An Ethnocentrically oriented person-(or group), is someone, who believes that his or her ethnic group/nationality, is at the Center of the Universe; that is to say, all other ethnic groups are insignificant or parenthetical, to that particular ethnic group. Ethnocentrism often views his or her ethnicity, as superior to all others and therefore, by its own (uniquely particularistic) logic, must view all others as inferior.
There are levels of Ethnocentrism which range from the folksy and unsophisticated type, to the more intellectual and sophisticated type. While the former has its problems and should not be minimized, it is actually the latter, which is far more sinister and problematic.
Intellectually based Ethnocentrism is more problematic because it is comprised of a culture (or country's) Intelligentsia, who are primarily responsible for helping to shape the historical and ethnic identity of their countrymen and citizens. While some parts of Ethnocentrism have positive characteristics, unfortunately, both historically and contemporarily, Ethnocentrism, has been and is still, an "us versus them" type of mindset. Ethnocentrism tends to be more associated with lionizing the so-called, perfect and incorruptible nature of a specific ethno-tribe, while at the same time, vilifying "the other"...usually, a country, a people, a race, a religion or a culture-(both near and distant).
In a way, Ethnocentrism, is the oldest "us versus them" mindset, which, sadly, exists into the present-day.
(Note: Mark Twain, who, in addition to having been, "The Father of American Literature?", was also a prolific Travel Writer. He has a great quotation, which, in my opinion, counters and challenges Ethnocentrism:
"Travel is fatal to prejudice, bigotry and narrow mindedness"....He was right).