Its more than that. The issue here is that the CCP fears that religion interferes with their monopoly on power. You should know that the CCP(like most erstwhile communist regimes) have full and total control of the country, state institutions, justice system, media, government etc. As such the party publicly puts itself above the state itself. In short, if you don't love the party then you can't really be considered a patriot or might even be considered anti China, since to them the party is equal to China itself. So how can you love China if you don't love the party? That is also the dilemma. For example the police, security forces and military are all taught to be loyal to the party first and foremost then the country. In short even the military has to be loyal to the party and its top members are also members of the party as well. So even the military is linked to politics as well. So this also creates a situation where you have to show total loyalty to the party even as a military person.
So coming to the issue about the party and religion and Islam in particular, since that's what we are talking about. The main thing is that the party is right to be worried about religion(i'm looking at things from the party's view), since the way the party has been formed, it leaves no room for any possibility of a parallel organised mechanism or institution which might have some sort of power and control that isn't in the hands of the party. For example in Islam(like all Abrahamic religions) its believed that there is a higher power which is the ultimate power and as such members ought to be subordinate/subservient to the power and live and follow laws/rules of their religious scriptures and that only GOD is the highest /sole authority in their lives. This also clashes with the party beliefs/doctrine. Since the party should be the sole authority in Chinese peoples lives and total loyalty ought to be shown to the party not another 'higher power'. This is also why the CCP is still firmly separated from religion and it prohibits it's 90 million members from holding any spiritual beliefs whatsoever. Since the party is wary that believers can one day be following their god rather than their Party. People forget that Anti-religious, atheistic principles are part and parcel of the formation and foundation of the Communist party(every communist party in the world, not just China), going back to its very roots.
It is common knowledge that Marx proclaimed that “religion is the opiate of the masses.” Perhaps less well-known is that he expanded upon the idea. “Communism,” Marx wrote back then “begins from the outset with atheism.” So this is something people should understand. Its not like CCP just targets religions out of nowhere, its an ideological belief.
The people's daily summairsed it well in one of their articles: ''Superstition is thought pollution and spiritual anesthesia that cannot be underestimated and must be thoroughly purged.”
https://www.reuters.com/article/us-...ls-against-spiritual-anesthesia-idUSKBN1CH06O
So i think the problem here is that the root of the problem in international discussion with China on religious rights is not a legal one, nor a cultural one. It is an ideological one. How does one convince a ruling party whose own edict for itself is to officially renounce religion to protect and respect the rights of others who wish to practice it? especially when it goes against many of the communist party own principles/doctrine and even sole hold on power?