3) The feeling I get (not a fact; just my impression) is that the Left is against the wall and in favor of open borders,
This occurs incessantly on this board...take the extreme views and claim they stand for the entire political spectrum.
People need to define "open borders." You have the literal, legal phenomenon of open borders or what I might call de jure open borders. This would be making a change in the law to allow anyone to unconditionally enter with no requirement to ever leave. I suspect that SH isn't going to use the term "open borders" to describe any position other than this one, and that is ok. I'm a stickler for precision in language, and there's nothing wrong with anyone else requiring it. I doubt that you'd find many Democrats who would publicly take that stance.
When conservatives describe Democrats as "open borders," they're really referring to what they argue to be a de facto open border or the idea that Democrats won't do anything meaningful to prevent almost anyone from entering and staying. They base it on these things.
1. Opposition to the wall. By itself, I think this is dumb. You can oppose the wall without being for open borders.
2. Signaling their opposition to border security in general. Many Democrats would disagree with this characterization. However, listening to those Democrats running for President, I hear very little rhetoric about border security. Basically, they bash the wall and at least in the case of Beta, affirmatively support removing physical barriers that previously had support from both parties. They don't offer much of an alternative to a wall to enhance security. If they do have one, they virtually never talk about it. They spend a lot more time talking about how much easier they want to make it to illegally emigrate to the US than about how they'd make it tougher to emigrate.
3. Decriminalizing illegal entry. That effectively makes "catch and release" official and absolute policy. No basis to take anyone into custody for only a civil violation. And of course, as Jeh Johnson explained a few weeks ago, repealing the law strongly encourages people to try to illegally cross.
4. Bashing deportations and immigration enforcement officers and agencies. Hillary Clinton started this when she promised to end deportations of anyone to who doesn't commit a violent crime. Of course, AOC and others have called for eliminating ICE. if you adopt these policies, basically if someone makes it in, he can stay unless he's a total monster. Though there are plenty of monsters in the world most people are not. Does that mean that any non-monster who can save enough money to hire a competent human smuggler can stay? If not, I'd like to see some evidence or at least some argument that it's not.
5. Expanding legal immigration without any clear limits. Do we draw the line somewhere, or should it basically be a free-for-all? Nobody really answers that. (Of course, our media never asks, so I can hardly blame them for not answering.)
6. Like Trump, they're not talking about doing anything meaningful to employers. I guess nobody gives a crap about this. My civil action is here for those who actually care. No illegal wage competition. No expensive deportation proceedings. They'll just go home.
7. Taxpayer-funded healthcare to illegal immigrants. Who the hell wouldn't come??
So is it "open borders?" Not in the literal sense. It's still going to be illegal to enter the US without authorization. They are just going to make it very easy to get away with it, eliminate the major deterrents to it, and not do much to you if you happen to be dumb enough to get caught.