I make an effort not to be "that guy".
I find homebrewers who come into a brewery and think they know more about brewing beer than the head brewer extremely annoying and far too common.
If it is any consolation, that guy has already annoyed everybody else in the room before he got to you.
+1 Same here. I go to a brewpub where I know the brewer, and he'll often ask my impression of a beer, and I give it when asked. But I wouldn't march in and presume to second guess a guy, or feel I needed to pepper him with half a$$ed questions, like some. When I go to a brewpub for the first time, I get the sampler flight of whatever is offered. Tells me everything I need to know about the place (and the guy).
I did this at a new brewery here in nebraska, first time there and had a flight, they all tasted terrible. I wanted to tell him but he never came over and asked how they were so I kept my mouth shut.
The difference here is, non of our beers are terrible.
Criticism is one thing, taking on a false pretense that you are more educated than the guy brewing the beer is something else. Most homebrewers would have no idea how to make beer on a commercial level.
I should add, 99% of the homebrewers I meet are super cool and very appreciative of my beer. I get homebrewers coming in to bring me a new homebrew to try about once a week. Some of my best friends are homebrewers. But every now and then there's one guy who is going to criticize everything because "he could do it better" or "this isn't to style" or whatever. come on - you guys all have that guy in your homebrew club, right?