Rush would have been 18 in 1969.....the year the draft lottery began. The others you mentioned would have been 23 or older in 1965 when the Nam draft began.....not likely candidates. I agree that Kerrey did his war effort and to my knowledge served well. And frequently this is a plus. Unfortunately, whatever wisdom he acquired from that honourable service has not translated to his politics....in my view.
At that time, 1970, most of us took the que sera sera attitude. If called, go, if not, leave it alone. We all knew enough returnees to know that it was nothing but a cluster****, certainly not an issue worth dying for, not in the 70s.