the problem is the ideological purity bullshit that's taken over. For example, the "two genders" vs "gender spectrum" debate. The liberals have made it clear that anyone who believes there are two genders (a pretty standard belief mind you, since the dawn of history) is now "rebranded" as some sort of Nazi-sympathizer. That's the attitude. That's the sort of thing that is driving the rise of alt-right media on youtube and similar. The issue is that when balanced sources are willing to discuss both sides of the issue they get labeled as "alt-right". Even Laci Green is called "alt-right" now, because she debated people outside the "sjw though bubble". I wouldn't even consider the people she was debating with as being that far to the right. Many of them are skeptics about social justice movements, but their politics tends to be pretty left-leaning, e.g. socialists, anarchists, atheists, etc. By calling Philip DeFranco* or The Amazing Atheist "alt-right" you're basically conceding an entire swathe of middle-ground to the "right" as their territory.
I think that this is a key point that this argument hinges on. When I hear conservatives talk about the "extremism" of Democrats, it's usually the gender and LGBT politics that they're referring to, along with the broader tendency to attribute social ills to discrimination and various "-isms". More specifically, I suspect that what makes "moderate conservatives" most repulsed by the Democratic orthodoxy is a perceived tendency that Democrats loudly beat the racism, sexism, and homophobia drums too readily over situations that conservatives don't believe they apply to.
If we imagine the three central dimensions of the Democratic party platform to be social justice, economic equality, and environmentalism, the aggregate party ideology in practice has up to now been essentially right-wing on the latter two and fairly aggressive with respect to the first. I think some here would readily give them the benefit of the doubt that they haven't been able to act with a free hand, but I doubt any of us would readily apply the label of "extreme" to the national Democratic platform in any sense. What I find most damning about this arrangement they've settled on is that the social justice dimension is the least of these aspects that can be directly improved by policy (largely only making progress in the courts and to the extent that society at large can be influenced by the Democrat-affiliated media) which meant that a widespread swathe of reactionaries were created in opposition to hypotheticals and strawmen without there even having been much concrete progress to react against.
For instance, how many times have we had the "I don't want to learn 40 new pronouns" conversation even on this forum full of socialists and anarchists? This is a frivolous concern and hardly worth considering since virtually nobody wants that, but strawmen non-issues like that have come to be one the principal ways that the official orthodoxies attack each other, and it bleeds into discussion everywhere. Conservatives continually get accused of being racist, sexist, and homophobic (for the record, I think this has some merit) but clearly don't agree with that assessment, while simultaneously "liberals" get painted by conservatives as being a bunch of pompous fools chasing flawed premises to ridiculous conclusions (and also for the record, I also don't think this is an unreasonable conclusion from that perspective). Both have at least a kernel of truth, but there's nothing of substance being said or gained.
I should add that maybe it sounds like I'm implying that the Democrats really are "too extreme" on social issues at least regarding strategy, but I'm not sure that's the best conclusion. If Democrats pivoted from social issues to an economic or environmental focus, I'm not convinced they'd fare better. We can already see how successful industrial interests have been in discrediting climate change (the phrase itself even now feels like a political by-word), and while I think there is dormant popular support for some form of socialism that could be awakened, it's clear the Dems are hardly going to be the ones to kick that beehive.