The intelligence community has always walked a fine line.The people "on the ground," or at the terminals as it were, doing the gathering and analysis, have nearly uniformly been good, honest, and loyal, barring the crap like Ames, Hansen, Walker, etc. The people in the middle have varied from extremely competent and conscientious long-term pros to career-obsessed mediocrities who would sway whichever way would give them a step promotion, but from what I can tell even that wasn't super common. There is a certain conservatism that naturally grows in those environments, but at worst it usually results in a reluctance to make a call without overwhelming verification.
At the top, though, whoo boy, all bets are off. At the senior level the politics has always been the bete noir of good intelligence work. My father worked in military intelligence during his career in the Army, mostly counterintelligence. Sent to Viet Nam in the early fall of 1967, his people were picking up clear indications of what was to be the Tet Offensive. So were tons of other people. The info went to MACV, then to Washington, and...nada. Somewhere in between the pros and the politicos, the message got switched to what Lyndon Johnson's people wanted to hear. We know the rest of the story. That's anecdotal (my side of it, not the actual happenings, which are pretty well documented), but it illustrates the temptations that the IC has always had at certain levels to shade the truth.
But actually undercutting a president is pretty rare. Maybe you could argue that Carter or even Clinton got some friction from the IC at times, but I can't really think of any case where the community either withheld info or actively if anonymously expressed its disapproval of the president. So if that's happening here, it would be pretty unusual.
So unusual that we have to balance the reasonable concern about the tail wagging the dog with the possibility that, in this case, the cure might not be worse than the disease. But, in general, I share strongly this sense of discomfort at the possibility of the system really going off the rails. Once the IC, or the Pentagon, or anyone downstream from the White House starts getting in the habit of playing kingmaker or what not, the path becomes perilous indeed.