When you change other peoples code, you must be VERY diplomatic. That being said, remember the saying: "Diplomacy: The art of saying 'nice doggy' while you reach for the pepper spray."
Sometimes it is easier to push the bad aside and do the whole task from scratch. Then you have "new improved". The problem is that it must be "improved", being "new" doesn't make it better. Unfortunately many projects fall into the "it's new" catagory, when the old was very adequate for the task at hand. Think: an old (manual) typewriter with carbon paper at a remote location without power works quite well for a page or so a week.