I very distinctly remember the world at that time. I was 1-A for a year but never called, the attitude was if you get called you go, if not you don't. Then the lottery came and I got a high number and the question was moot.
The US was not threatened, had not been attacked and, most importantly, was not fighting to win.
For the time that I was 1-A I was working a big construction job where the crew was a mix of WW2 - Korea vets and guys back from Nam. Not a single one of these guys thought it was a good idea to join to fight a war that we had already decided not to win.
They all knew my status and everyday asked if the notice came. They all hoped it wouldn't.
You don't have to like it or even believe it but that's how it was.
So you just refused to serve in the military?