I would suggest that the analogy is inaccurate and has to be judged by the norms of the period, and not one by a nation and government over one hundred years later that was brutal in the extreme and engaged in genocide as a national policy.
I would also suggest that the brutality of the Spaniards during 1808-1814 was the cause of the French retaliating, and the French did not engage in the atrocities that the Spaniards did, including brutal treatment of prisoners of war. If you would like examples of how the Spaniards treated French and allied prisoners, men, women, and children, soldiers and civilians, I can post them for you.
There was also a significant pro-French element in Spain which supported Joseph as king and supported the civil reforms the French instituted in Spain during the period, not the least of which was abolishing the Inquisition. And it should also be noted that the French opinion of the Spanish was echoed by the British of Wellington’s army.
The sieges were indeed brutal, and a good portion of that is because of the fanatical resistance of the Spanish civilian populations of cities besieged by the French, such as Saragossa. And you can compare the French behavior in sieges in Spain with those of the British, who sacked Ciudad Rodrigo, Badajoz, and San Sebastien whose populations were supposedly ‘fr iendlies.’
And another factor that can be taken into consideration is the civilian deaths, between 40,000-50,000, among the Portuguese civilian population that were forcibly evacuated under pain of death in the path of the French invasion under Massena. This was the policy of both Wellington and the Portuguese government and these civilians died of starvation and exposure behind the lines of Torres Vedras. There was little or no provisions taken to feed or shelter them. Again, there are two sides to any historical ‘story.’
The native Prussian undoubtedly did not like the French at all, but many of them were not willing to get shot at, and the Prussians had to use force to implement conscription in 1813 in some Prussian territory. The poet Theodor Korner made comment on that fact.
The Saxon infantry did in fact turn on the French at Leipzig, but their heavy cavalry certainly did not, nor did the Wurttembergers. What does that demonstrate?