It only makes sense. Newcomers can't assimilate into the culture unless they learn the language.
I keep hearing this 'assimilate' thing. This is total BS. What Muslims need to do is just learn enough Dutch to get by at work. Beyond that, they have right to enjoy the food, movies and clothes of their choice (aka culture) as long as it does not violate decency.
For example, I like cricket. You can call it my culture if you so desire. So using your assimilation thingie, you may think that you have the right to force me to not like cricket? And, I would say that is a BS. However, I have to exercise my common sense in my love for cricket and I cannot go around American parks ans start playing cricket with Brett Lee who throws balls at the speed of 100mph.