A majority of Scots (55%-45%) voted to remain in the UK in 2014, but the pro-UK side fought the referendum saying the only way Scotland could stay in the EU was to vote to stay in the UK. 

Things have completely changed since the 1st referendum. The lies and misinformation (Project Fear) has since 2014 been exposed. Not just lies about the EU, but lies about the promise to give the Scottish parliament/govt more powers.

A 2nd referendum is justified. Indeed the SNP govt has a democratic mandate with a clear manifesto pledge to hold a 2nd referendum.