No invasion by US military during the BoP.  His constant refusal to send in combat units to VN throughout his presidency despite repeated attempts by the JCS to goad him into doing so.  Refusal to send US military units to Laos.  Refusal by JFK to bomb and invade Cuba during the Missile Crisis as the JCS and CIA and most ExComm advisers wanted.  The peaceful way he ended that crisis by the no-invasion pledge to Cuba and pulling out the missiles from Turkey -- LeMay and even VP Johnson, among other hawks, later muttered they feared the US lost in that exchange.

Then finally in his last year the attempt at a new understanding with Castro and at detente with the Soviets, which appeared to be reciprocated by Khrushchev, including, amazingly, Kennedy's overture to the Soviets to cooperate on a joint mission to the Moon (NK agreeing to it just 10 days or so before Dallas).  This following the landmark test ban treaty with that country, which was opposed by the Joint Chiefs.

As for withdrawing from VN, see NSAM 263 (order to withdraw 1,000 military advisers by the end of 1963 w/goal of ending our military assistance by 1965) as well as the testimony of most of the principals in his immediate national security chain who later stated Kennedy was getting out.  So did Maj Leader Mike Mansfield and leading antiwar Dem senator Wayne Morse who spoke with Kennedy in the Oval about VN just days before his TX trip.  Top aides Ken O'Donnell and Dave Powers wrote of Kennedy's withdrawal intentions some 40 yrs ago, the first to do so.

There's your motive -- any one of these major decisions, or most of them or all of them combined.  This was a radical departure from the Cold War mindset of the times, and groups like the CIA and high-ranking Pentagon types -- both virtually governments within the govt -- were accustomed to getting their warmongering way.

By contrast, as I pointed out last time, the WC could find no clear motive as to the accused LHO.  Nothing.  Nada.  Something you should have known about had you actually read the Warren Report as you loudly claimed to have done.

Re the coup against Diem, actually that was initially signed off on in late Aug, after Kennedy, on weekend vacation, was told erroneously by an assistant something at State that both McNamara and Rusk had agreed to it (they had not). Kennedy was trying to get a more honest govt in power there -- also honest and frank enough to tell the US to get out.  But he reversed himself on the coup with a later cable -- never revoked -- which said nothing was to be done until the US Amb to VN (Lodge) heard directly from Kennedy.

This order was ignored by Lodge and the CIA operating over there and Diem was toppled.  I have never read in any historical account of some later order from Kennedy overriding his last order stopping the coup plotting.

Do the Lincoln assassination researchers get together to agree on things like motive or the actual extent of that conspiracy and who was the ultimate mastermind?  Are the theories of the several schools there delegitimized just because there is currently a split as to the nature of the conspiracy?

You seem to be craving certainty and finality.  Neither is likely to be found re the events of Dallas, at least in our lifetimes.  It's too controversial, too important an event, too risky to be totally investigated at this time.  A few powerful governmental groups would prefer not to investigate -- their very existence would be in jeopardy if the full story were revealed and they would greatly prefer to keep the power they now wield.

In my opinion, the case for conspiracy crumbles from a lack of a single clear motive.

Alliances are formed for reasons that benefit the parties involved.  The "motive" of each participant for such an alliance does not have to be the same for it to be effective.

That's not a difficult concept.  

I don't purport to know what happened.  But I'm not going to rule out conspiracy any more than I'll rule out the lone gunman. How can I when all of the evidence has not been made public?