Paternalism vs. Tolerance
What is the best way to integrate immigrants into European societies?
First of all, the question is whether it is necessary to integrate them in the first place. The trade-off is one between freedom and security. Does the immigrants' choice to segregate themselves threaten the security and well-being of the wider society? Should we tolerate the immigrants' way of living as long as it doesn't hurt us directly, or should we pursue the integration objective for the immigrants' own good? Do we want to dictate what is best to a group of people even if their choices do not have a tangible affect on us (yet)?
Much similar to the question of mutual reflection and transformation I tried to address in "Europe," both sides need to be flexible and adjust themselves. As Milan rightly pointed out, immigrants have the responsibility to show an effort to adapt to the society they are in, but they can only do that if they feel welcome.
Prohibition won't work, precisely because it requires only a one-way adoption of European values by the immigrants. We should ask ourselves how we would feel if we were asked to abandon something dear to us because it is "backward." This adds insult to injury. It is only me who can decide whether it will be better for me to reform my way of living and expressing myself. I don't want to be dictated anything by those who think they are better than me.
Instead, as Anna rightly pointed out, policy-makers should ensure that immigrants mix with the locals from an early age. Immigrant children should go to the same schools as the locals. Immigrants should enjoy equal opportunity in the workplace and public space. This is the only way locals can influence immigrants in a real way. This is the only way they can exercise their "soft power." Well educated immigrants with a good income do not have any difficulty integrating with the society they live in.
The parallels with the headscarf ban in Turkey is clear, I believe. The solution is not paternalism and prejudice. It is tolerance, good will and equal opportunity.