I don't know about the medieval or Renaissance periods, but E. P. Thompson's famous--and amazing--article "The Moral Economy of the English Crowd" (from the journal Past and Present, 1971) describes bread riots in early modern England. He argues that before the full development of capitalism in the 18th and 19th centuries, there was instead a "moral economy" in England that carefully regulated the supply of food. Farmers, bakers, and grain merchants especially were quite restricted in what commercial transactions they were permitted to engage in, what prices they could charge, and so on. Farmers and merchants, for example, were prohibited from selling on "samples" of grain or from carrying out "forward" sales--in other words, they had to buy and sell real shipments of physical grain that were present at the point of sale. You were not allowed to arrange to deliver something later or sell a grain "future." Bakers had to bake loaves of certain weights, with the weights being tied to the price of wheat or barley (there wasn't enough small currency in circulation to adjust the price of loaves, so instead they adjusted their weight, but the effect was the same).

The bottom line for all of these regulations was that the moral ideal was that a person would produce food for their own consumption, and the the links between producer and consumer should be as short as possible. Now, in reality, most people worked not as subsistence farmers, but produced for the market; most of these regulations were enforced sporadically, or ignored altogether. This was particularly true in the case of milling, which became a fully capitalist pursuit in the late 17th and early 18th century, and which fell outside the older legislation. The fact that British farmers' productivity was improving and that the British economy was relatively prosperous meant that people did not generally mind a whole lot that the laws were not strictly enforced.

However, in times of scarcity or crisis, these laws could be reasserted quite rigorously. At times, this could lead to serious disorder and bread riots. Yet it was relatively rare for the violence to be "senseless" or random; instead, the farmers or townspeople often went after the merchants and, rather than simply seizing their goods, would force them to sell at a "just" price--often well below market value, but right in line with the older "moral" economy. And, to answer your original question, in many cases, local nobles, even magistrates, would at least overlook such actions, offering tacit approval. In some cases, Thompson argues that local nobles even assisted and directed such actions. So, yes, there were certainly cases where nobles sided with the poorest elements of their society at moments of violent upheaval.

During the German Peasant Wars, the famous knight Goetz von Berlichingen briefly led an "army" of revolting peasants.
According to his later defense he saw himself partly forced to do that and partly he he wanted to prevent violent excesses.