The liberal argument would be that they are protecting the cultural identity and values. The right wing argument basically would come down to saying that muslims who don't believe in secular democracy and wants to replace secular democracy with khilafah should not get freedom in secular democracy. And this basically is the argument of right wings groups. That if they dont get rid of Muslims from Europe then soon under Islamic rule they non-muslims would be treated as rats. That none of the rights Muslims now demand from them would be given to them when muslims rule. That those non-muslims who now support Muslim rights would be treated as second class citizens when Muslims get power. And i see this argument every time you argue with islamophobes. And I sense something wrong in supporting secular democracy in one place but considering it shirk in another place. Anyways, these are deductive arguments. It will be better in clarifying the presuming Islamic ruling on it before trying to make a coherent understanding of this. Brother tripoly Sunni can start a new topic on shariah ruling for non-muslims displaying their religious or other symbols.