They aren't "Dems." They are Dems. For West Virginia, Manchin is left-leaning. Keep in mind that Biden did worse in West Virginia than Trump did in any state. That's how red it is. Having a Democrat from WV would be like having a Republican from Vermont or Massachusetts but even more out of place. Sinema is behaving the way someone from a purple state likely would.
Basically, they're both Dems, but they're not crazy. Furthermore, I've read that they speak for other Democratic senators who don't want to go on record and invite primary challengers. In fact, when the cameras are off, we know damn good and well that they speak for Chuck Schumer based on comments he has said in pretty recent years.
Ultimately, you guys have talked yourself into this idea that things like voter ID, going back to pre-pandemic election rules, etc. are such a major threat to the Republic that it's worth radical change to try to stop them. That's why the Bull Connor, Jim Crow, and Jefferson Davis references resonate with you. People outside your bubble hear that and think it's lunacy. It's just really hard to make people think "May I see your ID?" is comparable to firehoses, attack dogs, and lyncings, and when you guys invoke those things, it just sounds wildly hyperbolic and nutty - and to the point that it comes across as insincere and fake. Normal people don't believe it, and worse, they doubt your belief. You try to link them by bringing up January 6, but it doesn't logically follow. Feel free to keep it up, but it's not a winning formula. It alienates far more than it attracts or motivates.