Borussia Dortmund's win overshadowed by protests

After last weekend's organized protest in England over high ticket prizes from Liverpool fans, now that 'minor' incident is slowly crossing to Germany.
At the quarter-final stage in the DFB Pokal (German Cup) in Stuttgart fans protested against high ticket prices protest by staying away at the start and throwing tennis balls onto the pitch. Several thousands Dortmund supporters spent the opening 20 minutes away from their seats at the Mercedes Benz Arena with unfurling banner stretched across the empty seats by saying 'football should be affordable'. That however did not distract the club, who with 3:1 away win qualified for the semis.
Football fans over two countries now showed their anger against their club's management leadership. We now only wonder who will be next? Will this be global 'trend' soon?