"In other words, might makes right."
Oh for corn's sake. We have had the draft during at least two periods of our history without such extreme consequences.
You were not talking about the draft, but about "community service." The draft may be necessary for the common defense, which is a legitimate concern of the federal government; but forcing young people to do "community service" is not a power granted by Constitution to the federal government. Nor does such service comport with the concept of limited government.
Compulsory national service would not produce oppression on the order of slavery or the Holocaust. However, it would turn out to be just another monumental government boondoggle. There is no way that the federal government can employ tens of millions of young people in worthwhile pursuits; instead, their service would be wasted on useless, even counterproductive busywork.