So, to summarize: He's a far-right extremist from abroad. His agenda is to promote the deportation of foreigners from Germany and keeping foreigners out of Germany. The government officials found out about him and grant his wish by banning him - a foreigner - from entering Germany. And now he's mad, because... They did as he told them?
The leader of the PEGIDA movement that did many far right anti refugee demos in 2015 and 2016 had fled to South Africa in the 90s to avoid a prison sentence for multiple break ins. He then was convicted for robberies, drug dealing, scams, the whole ordeal.
Of course their main "argument" was that all refugees would be criminals and increase the crime rate in Germany.