raBBit, I think I made pretty clear that my problem was not with the idea of a US President trying to improve relations with Russia. No one is saying not to do that, so, let's drop that straw man. You are 100% aware of what people are upset about, and it isn't the idea of the two leaders meeting to talk, so stop with that game.
I can't get my head around the idea that any American can be OK with Trump, while standing next to the leader of a country who have provably and by all accounts been trying to undermine the US in any way possible (including elections), undercutting his own intelligence agencies. It is inexcusable, even if he does disagree with some of their assessments. It is inexcusable not just because it lacks patriotism, which isn't the point either. It telegraphs to the world that the US is incapable of operating in a complex foreign policy environment. How could you possibly think that is OK?
Secondarily, it also makes Trump look even more inept as a leader (though frankly the world already see him as a joke anyway). These are agencies he manages, run by people he nominated, and he's out there saying they are wrong about one of their most important focuses. If that's true (which it's pretty clearly not, but let's play along anyway), then Trump is a useless leader! Nothing in this makes Trump look competent, at all.
Finally, just to destroy yet another strawman, no. No, Obama, or Bush or Clinton or Bush or Reagan, would not have been feted or celebrated for doing what Trump did. They would be crucified, and rightly so. How do I know this? Simple - none of those previous Presidents ever did anything like this, because... it is 100% idiotic to do so. They wouldn't have. If it were actually true that they would be celebrated for it, then they would have done it, because all these guys have huge egos. Think it through, man.