I respect what many are saying about voting for McCain, and completely understand the logic. National security is any president’s foremost responsibility. Not all of us who are still skeptical about him want another attack, or want to lose the war. I just can’t stand the guy, basically, and abhor the fact that he’s crapped on a lot of principles out of pure selfishness. I deeply believe that he and Hillary are ALOT alike - both are self-serving, manipulative, egocentric, and lack character. Would he make national security decisions based on doing the right thing...or, just like any politician (and as he has done in the past) - make decisions based on politics? How concerned can he be about the security of the American people when he supports open borders?
There is also a coherent principled case against McCain, but it is an extremist one, far too extremist to be part of the mainstream of either Republican or American politics. I am thinking of nativist Buchanan types who are for protection and zero immigration yesterday, legal or not, who are fundamentally committed to Malthusian economics. I think that is an intellectual error, but there is a coherent ideological position there. It just has consequences mainstream conservatives are not willing to embrace (like, we aren't at war with Islam, but we are at war with Mexico; like, George Bush is a traitor; and similar extremist nonsense).
And there is a clear pragmatic case for supporting McCain as better than Obama, which can be summed up very easily - name one issue of interest to conservatives on which Obama is to McCain's right. Can't be done, and to me that makes it all dirt simple.
I think the first sometimes piggybacks on unstated instances of the second, avoiding spelling things out because of where they lead. I don't think most in the first camp are honestly in the second - they just have a visceral dislike for the man personally, for his long standing unwillingness to kowtow. Personally, I consider it among his best personal traits - kowtows are for pussies, not to put too fine a point on it. Some of that also goes back to the 2000 primary fight, when people deliberately tried to convince themselves there was some huge ideological difference between Bush and McCain.
In fact there isn't.
On your last point, people conveniently overlook that McCain was working for Bush's policy and top legislative priority, when he incurred the grassroots wrath over immigration. There isn't a dimes difference between them on the subject. The party base left them on the issue, not the other way around - the party stood for the same policy mix clear back to Reagan, and it is the base that moved out from under them, not the reverse.
That may be many things, but Republican apostasy it is not. It was simply supporting the position of his president. If we were smart we'd accept victory on the subject of border first and move on. If instead we try to make it a litmus test for all future republican candidates for anything, then we will simply rule more than half the party out, and exile ourselves indefinitely. At least half the party supported the pres on it. If they are all out of court because of it, then there isn't a party left.
In politics, when you win on policy you should pocket it and stop fighting on politics on the same point. It lets others come to you. Instead trying to ruin forever anyone who ever opposed you on anything, does not make them fear you or need you. It just makes you impossible to work with and not worth trying, and makes people run from your policy positions. This is doubly so if you then don't even reward those who supported your preferences in the primaries. I mean, none of the red meat anti-immigration candidates got out of single digits. Not a way to reward going with the grassroots against the pres on the subject.
How concerned can McCain be on security if he disagrees with you on immigration? Fully capable. Bush was and is. McCain would be, too. The only real difference between them on the subject is that McCain was for the go large solutions earlier, listening to and articulating the army brass preferences, against the sec def and go light types - which was the right call, and one that would have saved us several years of political grief. Though to be fair to Bush, also a tough call for anyone but a professional officer.