Yes, liberals in America are all smug and holier-than-thou, unlike their ideological opponents, who really listen to what you have to say and never judge you ahead of time. And, of course, they never pass comment on how a person looks.
Because what makes some of us on the left come off smug or haughty is the fact that conservatives refuse to accept that we deserve those protections. Worse still, some of them think that LGBT people should be put into some kind of hospital to be "cured" because "JESUS!" I'm not trying to lash out but it's a real complaint I have as someone who was formerly an evangelical Christian. It's a thread of thought I see that conservatives get looped into that their faith should override their sense of good law. I'm not asking for the Christian churches out there to let me join their congregations. I'm asking for them to respect my civil rights as I respect theirs. It's a reciprocal arrangement with both benefit. It's mutualism at it's best. Why is this so hard for them? I just want a good answer beyond their emotive, knee jerk reactions.
Oh, and religion & faith is largely based on emotion, so asking for something other than an emotive response from an Evangelical Christian is... misguided. (As far as I'm concerned, the Evangelical & Pentecostal strains of Christianity have evolved to be largely based on inspiring emotion particularly in their services, from the pop style worship music to the street preacher style sermons).
I'm a centre-left in my own country, which would be far left in the US. Gay marriage is a non-issue to me, because it doesn't affect anyone that is not involved and consenting. I'm of the opinion that if those religious people who oppose it because it brings the devil or some such, if they want to ban it because of their beliefs, then they should step forward and provide some proof. If you want to meddle in a stranger's life, there should at least be some evidence, rather than a hunch.
Unfortunately I don't have a good answer for you, apart from the intolerant christians simply turning to religion because of easy answers. There's plenty of christians in the US who don't bludgeon their neighbours with their faith, and those people generally are up for discussion. It's like the Church of England in the UK - they're christian, but they're also perfectly normal people that can live beside people who don't behave the same as them. But if you're the kind of person who finds asking searching questions difficult, then a loud defense of your religion helps keep you 'safe'.
As for the smugness, I find it hilarious when conservatives talk about how smug progressives are, even as they're using a dismissive tone as they describe that smugness. The main article is a classic example of this, and my comment was just meant to point out that both sides do this tactic that the author so despises.
Unfortunately, the only way to get people to change these kind of deeply-held beliefs is to get them to ask themselves questions about it, and they may get there of their own accord. But if the other side isn't listening, then those questions can't be seeded.
A shorter form of my opinions on gay marriage is this: it's fucking outrageous that a completely unrelated person can get in the way of a loved one making important decisions for their partner (like medical care). Is there a need for debate on it? No, not if you're for 'Freedom'. And, of course, if a person is not for 'Freedom', then they must Hate America :)
"[T]he contemporary debate within modern political systems are almost exclusively between conservative liberals, liberal liberals, and radical liberals. There is little place in such political systems for the criticism of the system itself, that is, for putting liberalism in question" (Alasdair MacIntyre, Whose Justice? Which Rationality?, 394).
Smugness is a problem for liberal liberals and conservative liberals alike. Perhaps smugness is a natural temptation or outgrowth of liberalism itself.
However, it raises an excellent point. The United States is not going to get anywhere if half the country looks down on the other half as a bunch of plebs, and in response the "plebs" disdain the elites. (I understand that this is a gross simplification, but I have seen this attitude often enough that it is significant).
For me, the article was about the need for mutual respect.
Ironically, the people who are going to take it most directly in the tuckus, are the people who voted Trump.
Clinton largely campaigned on shame and fear, and the midwest felt too left behind to care about that.
I don't even live in America, so it's not like I consider myself an American liberal. In fact, in my country, the Liberal Party are the conservatives, and being centre-left, I wouldn't identify with them either.