Why can't you be happy for us: Scottish independence and the English left

A friend recently posed this question:

Why is it that the English left is so comfortable with the independence of everywhere from Australia to Zimbabwe, but so bitterly and viscerally opposed to Scottish independence?

The Scottish independence movement has explicitly postitioned itself to the left of the Labour party. (The policies of the SNP in government are not exactly hardline socialism, but that's a topic for another post.) In the referendum campaign, the Yes side did not rely on narrow, reactionary appeals to blood and soil. Instead it adopted a progressive civic nationalism, arguing independence offered a better chance to build social justice in Scotland.

The nationalists firmly believe in the rightness of their cause. In theory, their fellow leftists in England should be natural allies. Yet in practice, the reaction has ranged from indifference to hostility. Why could this be?

I'm taking a broad definition of the "English left", including but not limited to the Labour and Liberal Democrat parties. It has the following reasons to oppose Scottish independence:

1. Electoral self-interest: Labour and the LibDems want Scottish (and Welsh) MPs to counterbalance the Conservatives. Obviously it didn't work so well this time, but historically it hasn't been a bad strategy.
2. Shared interests across the UK: They see themselves as part of a UK-wide movement which transcends divisions between England, Scotland and Wales. The latter two provide leadership and ideas as well as raw votes. Four of the last five Labour leaders were Scottish or Welsh (including Blair, born and raised in Edinburgh), as were four of the last six Liberal leaders.
3. Federalism: They support devolution, and may want to extend it to some form of home rule or federalism; but they don't see anything inherently oppressive about Scotland remaining within the UK. As previously noted, Scotland elects MPs to the UK Parliament, which Australia, Zimbabwe et al. never did, so anti-colonial arguments do not apply. (If anyone will get a raw deal under the Conservatives it's the north of England, who don't have a devolved government to protect their interests.)

Scottish nationalists may think any or all of these reasons are mistaken. But I think a large proportion of the English left believe them or something similar, so that's what they have to engage with.

There are exceptions, of course. George Monbiot and Billy Bragg have argued Scottish independence is just the shot in the arm the English left needs. In addition, it will be interesting to see how the left in England responds to the rise of the SNP in Scotland. Both Labour and the Lib Dems are still in shock from the general election, and I think it will take them at least a few years to come to terms with the defenestration of their Scottish MPs.

That said, I think the reasons I have listed above are strongly held and will prove difficult to shift -- if it is even desirable to do so.