This is how younger folk make a rod for their own back. You do not know the mans history and he is older than you so has worked through many changes, some he will not have agreed with like many of us. The bigger man will cut him some slack, show some respect, even if not the standard you aspire to. My not so humble opinion is that YOU show the way by quietly doing it better as it is clearly your opinion that you can. On one occasion, many years ago and a different trade observation on my part, a painter and decorator hung some very expensive wallpaper, there was room for improvement, the aspiring younger man actually took the client around the site to point out the flaws. Do you think that is acceptable? As I do not with your picture of his work it may not be perfect but as a relative new guy on the block you have many miles to travel before you sleep, if you make enemies you will be short on serious help when you may seriously need it.