In your opinion, and also in my opinion.
No it's not an opinion, it is a fact.
But that isn't the point - there are others who may consider a war memorial to be a completely pointless jingoistic homage to militarism, but would consider the Koran, and any and every copy of the Koran, to be sacred.
And they would be wrong, at least about the "every copy" part. That's absurd and a moment's thought would tell them that.
If you believe in free expression, then those people are just as entitled to their view as you and I are of ours.
People are entitled to believe what they want. What they are not entitled to do is coerce other people into their beliefs nor punish them for not toeing the line with respect to their superstitions.
My point is that were someone to vandalise something, in order to consider our response to that act we need to consider what is written (if vandalised by writing across it), the significance of the vandalised object to others and the motivation of the vandal. And in particular if the motivation of the vandal is to cause deliberate hurt/distress to people who consider that object to be of great significance and importance.
You are conflating "The Koran" wit individual constructions of paper and ink that convey the text of the Koran. If I burn Tahir Ali's copy of the Koran that's one thing. If I go out and buy my own copy of the Koran and burn it, that is entirely another and principles of free expression suggest I should be allowed to do it no matter who it offends.
And the prime minister should have answered "no" when asked if he was going to criminalise me for burning my own Koran. It's not making up policy on the hoof because, as you said, the government is not going to introduce a law against desecrating religious texts.