So there's no view a Democrat could express that wouldn't disqualify him in left-leaning folks' minds? That would be depressing. Winning isn't everything.

That depends entirely on the expressed views of the person they're running against. I accept anyone I vote for is going to do things I don't like. Maybe most things. Avoiding the vote because there's no candidate that's "perfect" leads to people getting in that will do EVEN MORE things I don't like, so while winning isn't everything, it's a lot.

Winning isn't everything, no. A "loyal opposition" is an important thing - I'd love to see Eisenhower/Goldwater Republicans balancing out the Democrats.

Handing over the reins to the crazies, though, is significantly dangerous, and all candidates are going to have downsides. Obama's been wrong on gay marriage in the past, but it's quite clear that his administration has been far better for gay rights than a Republican one would have been.

A related point, though, is that the opposition is almost always characterized as "crazy" at the time.

Goldwater was portrayed as a dangerous right-winger when he was around. The famous "daisy" campaign ad [1] was anti-Goldwater after all. This crazy man is going to kill kids in a nuclear war!

He did break from the Republicans later, and once he was no longer any sort of political threat, he magically became an icon of moderation or something.

It's worth keeping in mind that in the moment, the political opposition is always portrayed in the worst possible light. It's just how politics works.

[1] https://www.youtube.com/watch?v=dDTBnsqxZ3k