I also object to this hypocrisy. Parties will say in their defence that they do not have direct religious affiliation with the/a Church, and that the name only means to convey a set of values inherited from Christianity. I wonder what "special Christian values" they are defending that are not shared by other parties.
The Belgian constitution also states that no one can be taught religion against their will in state-funded schools. But in practice almost all schools, even those that are not Catholic-affiliated but purely public, teach Catholic catechism, and children aren't asked whether they want a dispense or not.
I sometimes feel that the whole system is highly hypocritical and that laws (even the constitution, which should primes over everything else) are just there as "decoration".