Sir Ming said in a recent interview that "there is a sense in which liberalism and nationalism are the antithesis of each other."
I guess he means that liberalism is partly about creating equal opportunities for all people, and that doesn't mix well with borders and national laws. However, I'm sure Sir Ming doesn't seriously propose to abolish all countries anytime soon, and if he did, he would be violating another liberal principle that says that decisions should be taken as close to the involved people as possible.
Scottish independence is not about building up new borders – Scotland is already a legal and political entity – but about removing a superfluous and top-heavy construct: Great Britain.
So long as Scottish independence happens within the EU, there is no reason to assume it would violate any important liberal principles.
Besides, if Scottish independence is so terrible, is Sir Ming implicitly asking for Ireland and all the British colonies to come back to the UK? Surely Scottish independence isn't any less acceptable for a liberal than Irish independence?