Digs (and opinions) work both ways. In this case the 'dig' was specific because the poster concerned has a habit of doubting the education of those voting to leave the EU - and in a slightly unpleasant way.
Based on evidence:
http://www.telegraph.co.uk/news/201...e-results-compare-to-the-uks-educated-old-an/
This was a pattern that was reflected in the results - with the Brexit vote correlating with areas with high shares of people with no education.
Only three of 35 areas where more than half of residents had a degree voted to leave the EU - South Bucks, West Devon, and Malvern Hills in the West Midlands.