By 'populism' you mean 'people speaking their minds'? And that they should be ignored?

By 'populism' do you mean the vast majority of Europeans and clear majority of Germans who are not supportive of the 'open doors' immigration policy?

Especially those made by diktat - without popular consultation, without legal consideration, without a vote in parliament - which affects the entirety of Europe?

Maybe Germans can have their 'leaders' stop forcing policy on the rest of Europe?

And by the way - your argument does not work in your favour: it is not the AfD telling people to prepare - it's the actual government wherein there is no AfD people to make such claims.

The very fact that the government - weary of people acting out against Muslims - is willing to make this statement says a lot about the actual threat environment.