He had written that some poor folk who are able to vote barely even know their own names. This is true. No age-range was mentioned.
In any case it is compassionate rather than critical. Equally he did not refer to No voters as Quislings – he tweeted a link to the satirical website BBC Scotlandshire which contained, with much else, a fantasy item about a Quisling Dinner.
That website takes its name from the impression that parts of the UK establishment, including the BBC, treat Scotland as a county or shire. Whether that impression is justified and whether the website is entertaining are matters for individual judgment.