That depends on your valuation of Brexit itself. If being part of the EU actually is a core value in Scotland then a referendum would be fully legitimate. If it's not then Brexit is just a convenient pretext. On face value the vast majority of the Scotts want to stay in the EU. So it's up to Unionists now to prove that this is less relevant to Scotts than being part of the UK. You may or agree with Sturgeon or not, but it is she who has the numbers at this moment in time.
Congratulations America