That would be a massive miscalculation. Southerners would see it as a war of survival, and Northerners would put patriotism over abolition (outside of a few). Abolitionists would be viewed as unpatriotic.
As I saw it, if the question
Can the people of a Territory in any lawful way, against the wishes of any citizen of the United States, exclude slavery from their limits prior to the formation of a State constitution? can lose someone the presidency, the question
Should Federal troops be used to protect property in slaves? is going to cause someone serious problems at the very least.
The RN might burn a naval dockyard which might get out of control but beyond that burning cities is not a mid Victorian thing.
We don't have a lot of evidence to conclude either way, to be frank. I'll assume that American advocates will insist we discount Kagoshima and Lagos because of the colour of their inhabitants' skin, which pretty much leaves us squabbling over the events of the Crimean War. During the war, the British focused on low-collateral, high-value targets: fortifications and naval stores. Even if the British limit themselves to this kind of low-level raiding- burning stores deemed contraband, running off slaves, inspecting coastal traffic, etc.- there are going to be a lot of unhappy people.
The reason for the decision to avoid civilian casualties was in part due to Captain Bartholemew Sulivan, the hydrographic officer, who handed out Bibles to Finnish islanders and blocked attacks he thought endangered civilians, and in part due to the French, who vetoed a British proposal that Odessa itself be attacked as well as the forts surrounding it. There are suggestions that the latter was because Napoleon III planned to use Odessa as his base of operations when he took personal command of the French army in the Crimea. It would be ignoble of me to imply that the reason Helsinki is not attacked is because Royal Navy officers had a habit of attending balls in the city, but I'm just flagging up that that went on.
More importantly, there are indications that this humanity is not a ubiquitous attitude. I've not dug into editorials, but a quick perusal of Hansard reveals the following:
I ask, Sir, why is this particular indulgence to be shown to this enemy? What has been the policy of the British Government with respect to him? What are we to understand to be the wishes and the feelings of the people of this country upon this point? We did commence this war by exercising peculiar forbearance, and Admiral Dundas, having it in his power to destroy the city of Odessa, yet spared that city — he attacked only the batteries. There has been something like censure even cast upon him for his forbearance, and I must say, that I myself may now begin to partake of that feeling... Whether they be Fins or whether they be Russians, we have offered them battle on the open sea and upon fair and equal terms, and they have declined it... Well, I say, if they will not meet us on the open sea, we must visit them in their own homes, and teach them that a war with England is not to be engaged in with impunity. (Sir James Graham, First Lord of the Admiralty 1852-1855, HC Deb 29 June 1854 vol 134 cc920-21)
Had Odessa been Rome, Naples, or Athens, I can well understand the feeling which might have prompted us to spare it. But Odessa has no historic fame—it is not the repository of art. It is nothing else but a great depôt: one of the granaries, not only of Russia, but of Europe—a station for troops, and the place from which the Russian armies, both in the Crimea and Bessarabia, and, consequently, those engaged in an attack upon Turkey, and in war with us, are supplied. I respect that feeling of humanity which might have led you to avoid, if possible, a bombardment. But what, under the circumstances, would have been the proper course? It appears to me that you might, consistently even with your principles, have summoned the garrison to lay down their arms, and to surrender the granaries and military stores within twenty-four hours; and have declared that, in the event of refusal—giving them that period to send out their women and children—you would have used force. Do you think a Russian fleet would have spared Liverpool or Hull? (Austen Layard, HC Deb 12 December 1854 vol 136 c183)
Why did not our fleet raze Odessa to the ground—the granary of Sebastopol? (Admiral John Walcott, HC Deb 16 February 1855 vol 136 c1467)
Why had Odessa been left undestroyed? Had not subsequent events—had not the operations at Sebastopol—made it clear how unwise it was on the part of the Government to leave the town of Odessa untouched? Was it respected because it was a commercial town? But Odessa could hardly be regarded merely as a commercial town, when they found the extent to which it was fortified—when they found a large military force constantly established in it. (Sir John Pakington, First Lord of the Admiralty 1858-9 and 1866-7, HC Deb 12 December 1854 vol 136 c113)
Furthermore, I think we risk discounting the way in which attitudes can evolve in wartime. If you had suggested to the average citizen of the North in 1861 that winning the Civil War would require uncompensated emancipation and a 300-mile swathe of destroyed houses, mills, railways and telegraph lines, you'd have received much the same puzzled look as if you'd told a British person in 1898 that they were about to lock up half the Transvaal.
