Obama is detrimental to a far larger number of people. Socialism always is. Dodd Frank and Obama care is far more damaging to far more people. By the traitor, Justice Roberts. The most damaging part of the bill was not the individual mandate but allowing the government to step in and actually limit profits and dictate corporate spending. The longterm human affects of those actions are going to be a lot worse than what you have mentioned. Add in Dodd-Frank, if it is upheld, then the government is cleared to totally implement a socialist agenda. How many people have socialist killed during that same time period you mention? The number lynched in the US is not even a significant portion of a single percentile of the deaths associated with socialism. The dust bowl, sure bad deal, but 2 milllion homeless, 7 thousand starving to death, not even a busy day for Linnen, Stalin, Mau, Minh, etc. Hell, not even a significant percentage of Americans at the time either. How many died fighting Adolf Hitlers National Socialist (Nazi's) in Germany? Since the first attempt to implement socialism, how many have become homeless and starved to death as a result of attempts to implement such policies? Was Slavery a bad deal for those under it, sure, but that doesn't change the fact that the vast majority of them would of been killed or never existed had slavery not existed. By far, most slaves were sold to Europeans by Africans who captured them in tribal warfare, prior to selling them to Europeans, they were simply killed or enslaved in Africa. Genocide is not anything new in Africa, only the lack of it would actually be a change in their history.
The Native Americans, well, they got their asses royally kicked because they practiced a form of socialism and never progressed above early stone age and couldn't compete with far superior technology and methods, thus, in the natural order of things, they faded into history. Further, after the US was formed, they stupidly started wars against it and got their butts kicked. No claims to "Indian" terreritory ever derived from the US, the US purchased or got those claims from other countries. They set a really good example, never let your military capabilities and technological advancement fall to such a weak level, someone stronger will come along, kick your ass and take what you thought was yours. The native American wars should of been against European and other powers, not the US.
Their is no significant difference in how bad a particular act was, but there is a major difference in the scope. Getting lynched in the US was probably a lot better for the individual than ending up in the Gulag in Russia.
PS. One of the greatest things about the Cold War era was that we got to train for, plan for, practice for and even sometimes we got to kill socialist. There is no greater enemy to mankind than socialism.