I gave him credit for that. His first command, PT 109 was sunk on one of its first combat patrols being rammed and sunk by a Japanese destroyer. Kennedy declined returning to the US afterwards and was assigned command of PT 59 and served honorably commanding that boat. He deserves credit for that. But, he was also, singularly, the only President that twice got us within a hair's breath of a nuclear war (Berlin Crisis and Cuban Missile Crisis). On that score, he loses marks. He was also a well known philanderer.
I'll add Clinton and Trump share many common traits. Both are liars... kind of goes with being politicians. Both are real estate scammers. Clinton, far more than Trump, but not to exclude either, are draft dodgers. They're both philanderers. Basically, both are pretty much human scum. But, that said it doesn't necessarily make them bad presidents.
Carter might have been a naval officer, but he was a truly lousy president. Nixon, Bush I, and Ford were all naval officers too. I don't see that as a particularly a qualification for office. If anything presidents who were previously army officers have proven usually better in office. We had only one air force officer as a president Bush II, and he wasn't anything to write home about...