Ok, if you are being genuine rather than flippant.
People are outraged because it is This tree.
It is part of a World Heritage property, protected by the Ancient Monuments and Archaeological Areas Act 1979 and also through the Town and Country Planning Act 1990 (Listed Buildings and Conservation Areas), which covers protection of the 'setting' amongst other things. It is not just a bit of odd vandalism, it is vandalism of a monument and listed property, and it is a crime.
Beyond that, the tree is iconic and a big part of shared cultural heritage. It appears in art, films, music videos, photography, painting, literature. It inspired people, lifted people's spirits, attracted and wowed visitors. It was cared for by some (employed to do so), and cared about by many.
It is a significant loss, to a place, to history, and to cultural references, and to some people's affection.
So no, it doesn't really compare to 100s of other trees, felled with permission (or not requiring permission) to make way for approved development decided by someone as being needed and appropriate.
There is a discussion there, of course, about the merits and deteiments of the removal of those trees too. But it is not really a discussion for this thread, or particularly relevant to this tree.