This is actually a very good point, and one could argue that we're already seeing this in our current society -- many people hardly use their brains and live in a purely vegetative state. However, the question then becomes -- will these apathetic humans be content with their lives or not? Because if they are content with some soap operas and porn and the occasional B-movie then they won't have reasons to riot and kill. However if somehow they become discontent and desire more from life, will they choose to better themselves or to "take" it from the ones they perceive as having more? I guess this mostly depends on the political environment at that time; as so many other times in history, if enough propaganda is leveraged the masses (especially the otherwise apathetic ones) can be warped into a frenzy of destruction. We can't predict if and when this would happen, only try to prevent it when we see the signs -- and the best weapon is education (not the public-school type unfortunately, but the Internet can play a huge role here).
Yes, agreed that people will need something to do. But what about virtual realities in this case? We already have tens of millions of people playing games like WoW, and if anyone has ever tried such a game you can tell it's mostly a simulacrum of work with a little fun in between. Grind, grind, grind, sell & buy, grind, do a raid. Rinse and repeat the next day I think more advanced versions of this will undoubtedly appear in the next few years and they would be a great avenue for people with otherwise no occupation to expend their mental energy.
Sorry, but that's wrong on so many levels... First of all, the Great Depression was caused by a complex combination of events which had a global impact, affecting countries with various types of economies. The pain and suffering was compounded by ecological and political crisis, and many historians argue that some of the statist measures being enforced (such as restricting international trade to "protect" the local markets) actually worked against recovery, deepening the economic meltdown. In any case, even taking all that into consideration, the amount of people directly affected by communism is an order of magnitude higher, you just can not compare one with the other.
As for the victims of WW2 -- the aggressors were all statist regimes (fascism being a close relative of communism), the most you can blame the "free-market" states like Britain or the US is that they tried to keep out of it as much as possible (which turned out to be a bad idea in the end).
As cool as Baxter is, and as useful as it can potentially become, it still can not do all the things you describe. It is only able to learn and repeat simple tasks. Knowing a thing or two about robotics, even that is an amazing achievement -- but way short of the robots you describe that will completely replace humans. For one, it is completely unable to move around by itself -- and that's not an easy problem to solve. Will it evolve? Certainly! Will we reach a point when it can do all those things? Probably. But that time has not yet come, which is also evidenced by the fact that factories around the world are not yet buying them in the millions. Do not underestimate the difficulty of getting there; when that happens, we can have this discussion again.
Now that I will not deny -- the concentration of power and wealth in the hands of very few individuals has become clearly disproportionate (some wealth inequality is normal and to be expected; the amount we have at the moment however is not). But is that a failure of the market or the result of statist laws and regulations and the expansion of government power? The evidence points quite clearly to the later in my opinion. Also, please remember that while power concentration may happen in a free market, it is a guarantee when you talk about a communist state. There you don't even have the choice -- the elite has the power "by law" and that's it, end of story.
I'd say there will be just enough of these jobs to provide a level of subsistence to a good portion of the population. Keep in mind that there will be jobs created in such an economy which we can't even imagine right now.
This is certainly true for simple, repetitive tasks -- humans are terrible at those while robots will excel. But when talking about the more complex, creative jobs that you envision will be taken as well? Not clear, not clear at all. A robot that will have a "hard AI" level (required to perform the most advanced human jobs) might very well suffer from mood swings, compulsive behaviors and the need to "take a break" from time to time just like humans. I have a feeling we'll be surprised how close to us these truly intelligent machines will turn out to be.