My understanding of this is that it is not really a serious proposal with any chance of passing. Rangel did it to make a point that the people fighting the war are disproportionately poor and they sign up for military service because they don't have many economic options. His idea is that if military service were compulsory, then you would have a better economic cross-section of people going off to war --- rich kids would get drafted too, supposedly. So it's not really a Democratic policy to reimpose the draft, it's Rangel's way of making a point.