Eisenhower warned the nation about the Military Industrial Complex. We didn't understand why VietNam was important to us, but trust in the government was still high. In those times, there was a kind of unofficial code about what was acceptable avoidance of the war. Using and embracing valid deferments was considered acceptable. Signing up for some other military program was considered okay. College deferments were considered okay, as long as they ended after four or five years to finish college.
What wasn't okay is when it wasn't fair. There's some question if either McCain or GWB were qualified for the programs they entered. With McCain, there's another question he doesn't bring up. He graduated from Annapolis in 1958. At that point there was no expectation that he'd end up in an unpopular war, so we don't know what he would've done if he faced the dilemma those younger people faced. At that time, it was considered bad form to take a pilot-training or Academy slot from more qualified candidates.
The war didn't end until the lottery system came to be and everyone's friends and loved ones had the same risk of being drafted.
McCain criticizing President Trump but not Romney, Gore, Clinton and younger pols (Ryan, Obama, Cruz, Rubio, etc etc) for not choosing to serve shows how off-the-rails Senator McCain is.
I seem to remember obie saying that he considered enlisting but by the time he was old enough VN was already over so...... Yeah, okie dokey.