"If Downing Street agrees to hold it, Yes start as favourites. If Theresa May blocks a vote, the nationalists' big argument is only strengthened."
It's kind of sad that Scotland has to resort to threats with secession in order to have its arguments heard in London.
Seems like now both May and Sturgeon are in a stalemate. Theresa wants to ignore the Scottish and Ulsterian vote, and in turn these guys cannot allow that to happen because they'd look like empty pawns. So ultimately, something has got to give. Either a compromise has to be reached, or this will escalate.
That said, I'd say it's a bit too early. Perhaps Scotland needs to wait for at least a few more years before they make another attempt, or until a time when there is absolute consensus in Scotland that this is what they want to do. If she does this now it would look hasty and desperate. And the question would arise if a third referendum wouldn't be likely shortly thereafter, and this makes the whole point of referenda kind of... well, pointless. But there is obviously tremendous support for independence in Scotland. It is understandable that at this moment the SNP would like to exploit widespread anger over the EU referendum north of the English border. The nationalists also have most of the seats in the region, so they sure are feeling emboldened.
In any case, Brexit itself, no matter if they opt for the soft or hard version (more likely the latter), is a major constitutional change for the UK. And let's not forget that Scotland voted overwhelmingly No. It would've been naive to expect Scots complying with what was mostly an English decision without any reaction. IMO, such a huge constitutional shift definitely legitimizes demands for an independence referendum. The PM begged Scotland to stay at the 2014 referendum, and kept repeating the point that it was a union of equal nations. That Scotland had a completely equal status to England in the union. If an issue such as leaving the EU has to be decided and it's good for England but bad for Scotland, then some kind of compromise has to be reached, otherwise how are the two nations equal?