It has become quite common for people on all sides of the political spectrum (but especially on the far right) to defend their positions by referencing their opponents. In recent events, Trump’s travel ban has been explained away as the same thing Carter, Obama, Regan, and Bush have done. In simplest terms, this is exactly like a child who, when caught doing something they know is wrong, immediately list everyone else who is allowed to do it. The phrase, “if everyone was jumping off a bridge would you do that too?” has become a cultural cliché to embody the ignorance of this argument.
Formally known as Ad Populum, or “The Appeal To Common Practice,” this fallacy is especially damaging, as it can be used to explain away any crime, as long as they can find the slightest parallel on their opponents side. Take, for example, a hypothetical future time where a group of people, such as Muslims, are considered an immediate threat, and the government decides to put them all in internment camps. The conservative administration (or at least their common man allies) would remind us the FDR did the same thing to the Japanese in WWII, so we cannot possibly view this as wrong. Obviously, wrong is wrong, regardless of the political party. FDR was just as immoral in this instance as our hypothetical future tyrant. This is the problem with this flawed thinking; acts are no longer judged on their true value as long as you can rationalize anything as the norm.
Actions must be judged by their value, not by their sponsor. It is too easy to lazily follow whomever we believe to be the lesser of two evils and accept whatever they say. Now, more so than any time in recent history, we must remain vigilant.