There could have been many temperature spikes--both cold and hot-- in the early and middle Holocene. Many could have been far more dramatic than what we are apparently experiencing today. This cannot be ruled out..But if there were such spikes, that makes an even stronger case for addressing manmade warming, because it's known that modern warming can't be explained solely in terms of natural factors.
So if there were the possibility of such spikes, we'd have to worry about them adding to CO2-caused warming and causing even more warming.
Also, it would be suspicious, if this were all natural to have all those spikes throughout the Holocene, and to have our period have a strong upward spike. Why an upward spike now? Why not a downward spike, or neutral conditions?
It's absurd, in a field like climate science, to say you can't compare two time series unless they have the same resolution. There is no perfect data, especially in climate science, which isn't an experimental science. You take the data you can get, and do with it what you can. It's a completely obvious question to ask how a reconstrution of the Holocene compares to the modern instrumental record, and that you can't answer it with the rigor of a pure mathematician doesn't mean you should compare what you can. And if you can't keep in mind the limitations and uncertainties of each piece of the larger time series, maybe you should following another field. Because the question of how does the last century compare to the Holocene is important for science, and beyond that too.