Christianity is currently the largest and most influential religion in the world, with a history of extreme and ongoing persecution, oppression, and abuse towards women.
Can I ask why you’re not concerned about the influence of Christianity but are about the influence of Islam? Is it because you support Christianity so are OK with the abuses carried out in it's name?
In any case, it’s not naive in the slightest; it’s just sensible not to be worried about something that isn't going to happen in the UK.
Islam isn't predicted to become the largest religion globally until towards the end of the century, and even then, it won’t be a majority. In the UK, it’s very unlikely to ever become the majority religion—certainly not within anyone on this forum’s lifetime.
As I said, society and cultures aren't static, a hundred or so years ago many people where disgusted by the idea of women having the vote or people being openly gay but it happened anyway. If Islam does go on to become a world conquering religion in 100 years time then there's not a great deal you'll be able to do to stop it.
Unless you're advocating for the persecution of Muslims in western countries to prevent it spreading further, of course?