It's the way it's done that counts. Being a sardonic dumbass and trying to point out that Ash is a shitty tuner doesn't enchance Spee's image whatsoever, nor does it make him look like an unbiased individual that is strictly pointing out troubleshooting errors in their tune. Im not saying Ash is an engineering gift from the Gods, but he's done a whole shitload more for the Z community than Spee will every do - so give him some credit for catching a mistake before he blew the guys engine.
"Losers always whine about doing their best, Winners go home and screw the prom queen"