To all those calling / writing / asking-questions-of-at-town-halls their representatives, this may help if the representative in question is across a party line: How to bridge the political divide with better moral arguments.
(I'm going to summarize and interpret things here, but I Am Not An Expert; I strongly recommend that you listen to the podcast episode, or watch the YouTube video embedded in the page I linked, to hear what the actual experts say.)
It's an episode of the podcast You Are Not So Smart, which tackles topics in the science of self-delusion. The big takeaway of this episode in particular is that the moral values which are important to liberals and conservatives differ in some fairly predictable ways – liberals tend to place more importance on things like equality, fairness, care, and protection, while conservatives tend to place more importance on things like loyalty, patriotism, respect for authority, purity, and sanctity. Because of this, constructing persuasive arguments in one moral vocabulary will fall flat on ears across the political divide.
(If you think, for example, that an argument against same-sex marriage on the basis of the sanctity of marriage has little intrinsic value, consider that gut reaction and place it into the experience of a conservative hearing an argument for same-sex marriage on the basis of equality. You can fuel your argument with as much passion or outrage as you like, and it will remain unconvincing. And if your goal is to convince, rather than to vent passion and outrage, different tactics will prove more effective.)
The other big takeaway: there is a way to frame most arguments using the other side's moral vocabulary.
So, a conservative moral argument against DAPL might appeal to sanctity and purity (we don't want to despoil our native lands; we want to keep our water pure, our lands beautiful), or patriotism and respect for authority (the construction of the pipeline along its intended route violates treaties the US has signed, and as a nation, we want to stand proud behind our stated word). A conservative moral argument against the Muslim ban might appeal to loyalty and patriotism (many of the people turned away at airports are in the United States as doctors, scientists, people whose work benefits the American people).
This is a persuasive tactic. But it may also be an experiment in empathy-building. As important as values like equality and fairness are to liberal communities, and as much as we think it's self-evident that all people should value them, appealing to someone in argument to change their underlying moral framework is unlikely to go very far. (Again, consider what your response would be if a conservative conversation partner launched an impassioned attempt to convince you to supplant your desire for fairness with a desire for sanctity. It might just be a non-starter.) Learning to identify and frame arguments in a conservative moral view can help build coalitions, and coalitions are good.
This will likely not help to build a bridge with anyone whose moral framework is "I serve my own ego and do what I want," but if those people don't listen, build the bridge to the people in a position to vote for or against them. Despite what pain and anger and wounded faith say, the Republican party is not actually one big mob of people who are hateful and spiteful and racist and sexist and evil all the way down to their core. Like any other group, they have their loud bad actors, and they have their people who earnestly value living a moral life. The fact that the morals are different doesn't mean they don't exist, and it doesn't mean that no common ground can ever be found or built upon.