Criminal damage is criminal damage all right, but they were acquitted by a jury of that charge. The defence argument was that the continuing presence of the statue, despite years of campaigning to get it taken down, was tantamount to a hate crime. The argument persuaded the jury. Grumbling about jury verdicts is fine and dandy but that's as far as it should go unless a miscarriage of justice (which means that the law has been subverted) is suspected. That has not happened in this case.