The Western ideal of religious tolerance is not shared by Islam, or for that matter China or anywhere else. In Islam, religion is so integrated with society that it would make no more sense to tolerate a plurality of religions than it would in to tolerate a plurality of laws. And so, when Muslims migrate to Western countries, problems arise.
In Western societies, the law makes a distinction between personal beliefs and public behavior. The state, in theory, does not regulate thoughts, but public order requires it to regulate behavior. When religious beliefs conflict with social norms, such as with the age (or even the requirement) of consent, Western governments attempt to enforce public order at the social level while respecting freedom of belief at the personal level.
This works only if the religious beliefs operate adequately at the personal level. But what religious beliefs behave like that? There is a Protestant conception of personal religion based on individual belief, but that's about it. It is not compatible with Islam (what else are we talking about, really?), where forms of dress, rules for worship, public prayer, marriage and sexual conduct, circumcision, burial, public ceremonies, and even the legal code itself constitute the essence of the religion. Private belief, the area that the government leaves unregulated, is peripheral.
Yet religious freedom is a core value for Western secular societies, where the government takes on the ironic role of enforcing freedom of religion by making rules on how to practice it. What is to be made free must be legislated, decreed, codified. Religious neutrality gives way to state regulation of religious life.
It is odd enough that in the act of protecting religious freedom, governments have to enforce religious conceptions. It is also impossible. The government that proclaims no limits on religious thought but only limits on religious expression creates an epistemic loop: it can never define the limits of what is not to be limited.
Similarly, in the case of marriage, or sex relations in general, the government enforces the freedom to wed or have sex. This is precisely the opposite of what homosexual libertarians of the prior generation wanted - they wanted the government to stop regulating marriage and sex. It is an interesting victory they've won, for what the government prescribes it controls, and what it controls it can proscribe.
The same quandary arises with racial equality laws. The state, having obtained the power through judicial means to require racial equality in civil life, would appear to have granted the wishes of the multiculturalists. But by the same token, the state is now practicing racial theory - a conclusion opposite to what the detractors of twentieth century race theory would seem to want.
Freedoms are dicey gifts, for gifts can be taken back. The freedoms in Western societies were not given to the Europeans, but were wrested from tyrants and wrought over centuries.