"I know some will disagree." I disagree. You were there for five years? Where?
From 2011 to 2016 I was in Germany every single summer, May and June. In 2014 it was the last week in April. 2013's visit in Germany was the shortest, ten days. I traveled solo on each of the five years in Germany, north to south, to the east, and to the Dutch border, took night trains on every trip except in 2013, saw nothing out of the ordinary, (anti-social behaviour), except that I could spot out "newcomers" I took RB trains and IC / ICE trains. You take enough of each of those trains, you can bet who is not going to be on which train. I was at stations late at night , esp Berlin Ostbahnhof ..nothing out of the ordinary
Last summer's trip I saw at Frankfurt Hbf announcements made in German then followed by that in English the Roma were working the station. I saw them at the station. You heard, " Achten Sie auf Ihre Wertsachen!" or, more often, "Lassen Sie Ihr Gepäck nicht unbeaufsichtigt!" You hear likewise at the airport...no big deal. In 2015 I did not hear those announcements.
Of course I am on my guard more now in Germany than I was 10-20 years ago, so what, still irrelevant, still Kindergarten compared to here. . That also depends where too. In the eastern part I was in towns where you yourself are the only foreigner in the streets and everywhere you go...Neustrelitz, Bautzen, Rheinsberg/Brandenburg, Frankfurt an der Oder, etc. I can spot out the "newcomers," esp these so called , punk wanna be toughs ( let them come to Oakland). You can tell by several ways that "they" are newcomers if you know what to look for.
"non-German" tourists... That description fits me exactly since the locals, and presumably the bad guys, will immediately see me as a tourist and a non-German. Who were these "non-German tourist victims?"....Asians, Italians, Spanish-speaking True, that in certain Hauptbahnhöfen I saw more of a police augmented by DB Sicherheit presence, some patrolling, others just standing and watching, ie, at Nürnberg and Hannover.
True, too that certain train stations are known to have negative reputations more than others, eg, mention Duisburg Hbf, see the reaction by Germans. Berlin Zoo isn't too appealing either, there is no practical reason to go Berlin Zoo (not even to eat). They should play classical music in front of Berlin Zoo just as it is done in front of Hamburg Hbf., constant classical music is what you hear.