It’s a horrible and hateful attack, and it may not be a coincidence that it was around Easter time, though since that also coincides with school holidays, it’s possible it’s a coincidence.
But “This clearly demonstrates that Christianity is under threat.from the secular lobby.” does not at all follow. The emojis and penis graffiti are much more kids/vandals typical than “the secular lobby”. Kids are quite capable of writing “god is a lie” - they are thoroughly indoctrinated at school about god, and many will reject it. It’s not high philosophy.
Yes it’s a horrible crime, a horrible attack. But it’s a massive stretch to say that this is some bigger picture that Christianity is under threat more than any bus shelter, graffitied building, vandalised school or town centre. Or indeed under threat more than any of the other religions in the UK.