An achievement isn't an achievement until you overdo it in this case.
if he farmed at slower pace, he wouldn't have had this achievement in first place.
Maybe to some, it's nothing to look up for. But for farmers, it is quite something :) but there are many other great farmers too.
You guys are just throwing tantrums at him while he can't even defend himself.
in my case, i just play along such assumptions because no matter the explanation, they will have hard time accepting it because they wanna stick to their mindset. ( goes both ways though :P )

