I talked to Andreas that very day and he is a big supporter of the European Union; the sentiment here and with many Germans is/was that the UK never fully committed to the EU by then/now anyway, keeping their own currency.
The whole Brexit thing is just like another death nail into the idea of a European Union and in the end is a clear sign of the right wing winning, brainwashing the UK into voting “leave”. It is a shame.
Of course there is a lot of polemic in that tweet that obviously did not gel well and can be rated as awkward, clumsy, depending on how much you know the person. If you think that “SchneidersLaden” which is not one person but obviously highly identified as Andreas or the guy himself is racist, nationalistic or anything like that, I can reassure you, he is not, totally opposite.
Also, I think the current SchneidersLaden team rocks hard but in the end you can discard my opinions and input here as invalid as I work for Mr. Schneider but not for SchneidersLaden. Patchpoint is bringing nice brands to Berlin, top job.