A horrible movement that has contributed to the destruction of the British Left.
In what way? Scottish Nationalism existed outside of the SNP (which itself was founded in 1934). The SNP had a disastrous election in 2003 in which the harder left; Trots and Greens were on the ascendancy. Labour began it's UK and Scottish collapse completely independently of the SNP (Labour have lost seats in 2001, 2005, 2010, 2015 and more than likely 2017; a long term decline). Labour's collapse enabled the SNP to win in 2007. They collapsed in 2011 entirely because of their own doing; their campaign was based on 'Now the Tories are back' and privately they had even decided on cabinet spots.
Then they sided with the Tories during an independence referendum. They even shared their
canvass information with the Tories. The Tories were the Trojans and they were the f-cking horse! Then they collapsed in 2015. Then they decided they would become defined by 'unionists' (which they never were before) and have aided and abetted the Tories to allow them to get leapfrogged by them in 2016. And now they continue to decline. And in their continuing Stockholm syndrome, they will probably end up in coalition with the Tories across Scotland.
Labour's decline both in Scotland and the UK is self inflicted.