This is Stuttgart, Germany. The stated reason for the protest is the overthrow of President Assad in Syria [1]. Last year, I remember seeing frightened children waiting to meet Santa as pro-Hamas crowds loudly protested about Gaza in a Canadian mall [2].
None of this should surprise us—according to Islamic doctrine, Christmas is considered 'haram.' Islam teaches that Allah had no son, and to believe otherwise is 'shirk'—the act of associating partners with Allah, a form of polytheism and an unforgivable sin.
Koran 19:88-92 'And they say, 'The Most Merciful has taken [for Himself] a son.' You have done an atrocious thing. The heavens almost rupture therefrom and the earth splits open and the mountains collapse in devastation that they attribute to the Most Merciful a son. And it is not appropriate for the Most Merciful to take a son.'
Additionally, even the sound of bells is condemned in Islam. Muhammad said, "The bell is the musical instrument of Satan" (Muslim 37:159).
Many participants in these demonstrations likely have no understanding of these teachings, following the crowd without question. However, to assume the organizers are unaware of their actions would be naïve.
These disruptions of Christmas celebrations should not surprise anyone—any excuse will suffice. Christianity is not the only target; according to Islamic doctrine, all non-Islamic faiths are subordinate and offensive to Allah. Unlike other belief systems, Islam offers respect in only one direction [3]. [1] https://www.bild.de/politik/weihnachtsmarkt-islamistische-rufe-beunruhigen-sicherheitsexperten-675c3471f09a33307f367b8f [2] https://www.rebelnews.com/anti_israel_protesters_christmas_demonstrations_malls_canada_palestine
If you ask me, I'd send those who sing Alh-Akbar to Syria, where they can join their friends and like-minded people.