Yes, the law doesn't allow harsh sentences in this case. It was a tree, not a human being.
I feel these two men were lacking in basic disrespect for nature. People cut down healthy trees all the time, it was just the mindless vandalism in this particular case for a tree that is very common (and can be invasive) in this country, was growing in this particular spot. A hundred years ago it was a sapling and was just left to grow in its unique setting.
I don't think the law is an ass in this case, these two men were, but whether others including pub chains or local councils, will cease to destroy trees at will I doubt very much.