I wrote about it here recently: Israel's ambassador to Denmark and the head of Copenhagen's Jewish community have both warned Jews in that city that if they don't want to be roughed up on the street by anti-Semites, they'd better not wear anything that would identify them as Jews – and, for good measure, they should also lower their voices when speaking Hebrew. The other day, in a supremely depressing article for Israel National News, Giulio Meotti provided a round-up of similar developments from around Europe.
For instance: a Jewish theological seminary in Potsdam has asked its rabbis not to wear yarmulkes in public. Pupils at a Jewish school in Berlin have been warned to speak German, not Hebrew, on school trips – and to wear baseball caps over their yarmulkes "so you don't give stupid people something to get annoyed about." Jews at Rome's main synagogue now remove their yarmulkes when leaving services; so do Jews in Malmö, Sweden. A Jewish teacher at an adult education center in Kristiansand, Norway, has been told "that wearing the star could be deemed a provocation towards the many Muslim students at the school." And so on.
The reason for all this cautious behavior, of course, is to avoid the fate of people like the Paris Metro passenger who, Meotti noted, was recently beaten unconscious by a mob who pegged him as Jewish because he was reading a book by Paris's chief rabbi.