Why would you want to identify with a political party where Trump supporters are at least 40 percent of the party?
We can talk about how absolutely despicable Donald Trump and the 44% of Republicans who support him are, but what does that say about the other 56% of Republicans who are willing to share a tent with such people?
We live, unfortunately, in a two party system. If we all become independents, we give up any say in the shaping of these two parties. If we all become Democrats, we let Trump and his ilk control half of the national discourse in this country (even if they receive well below half of the vote).
We stick around, we organize, we vote in future primaries, and we vote in the general (mostly for Democrats), until we throw out Trump, everyone who endorsed Trump, everyone who supports Trump, and every single cowardly politician who may privately hate Trump but refuses to speak out against him for reasons of political expediency.
This is the moral test of our generation, and all but a handful of Republican officeholders and candidates have failed it. So we vote for Democrats and pick up the pieces in 2018.
I do understand how ludicrous this is; if I thought a third party or the destruction of the Republican party were considerably more viable, I would advocate those options instead.