What did DHH do? I've seen some of his youtube videos and he comes across as a super reasonable person.

He wants to shoot Roma

You can go to his blog and read for yourself in his own words about what he wants to do with certain ethnic minorities in European cities. The exact suggestion he has is "what one does when there are too many wolves". The man is pure human waste.

He's also a vocal supporter (see his blog) of another piece of filth, Stephen Yaxley-Lennon.