Try looking instead at the comments by Ahmed - beginning at around
#311, say. Orci invited him to offer up some of that aforementioned "honest criticism," but Ahmed didn't seem especially interested in doing that. Subsequent comments by other posters suggest that Ahmed has something of a history at TrekMovie of being rude and unpleasant to others, and that they weren't at all surprised to see him doing so in the "Star Trek is broken" thread.
To be honest, reading Ahmed's comments from 311 to being told to fuck off just by themselves (there might be other contextual points but you bring that poster up specifically) he just doesn't like Into Darkness, and considers it illogical. His opinion is a bit bluntly stated but I've seen far, far worse said on other forums about Trek and other things without the creators being so unprofessional as to be rude and say "fuck off". It's as simple as not going on the damn website if you don't like the opinions people express.
Orci has been participating in discussions on that website and others for the last several years and has always shown himself to be willing to listen to opinions and answer questions. He may (and, as concerning spoilers, does) decline to answer questions in other than very general terms, and he has been known (whether politely or sarcastically) to shoot down opinions with which he disagrees or which he believes faulty.
Orci is quite at home in internet discussions and most of what I've seen at TrekMovie over the years (including the overwhelming majority of the thread under discussion here) has been pretty friendly and often a lot of fun. Orci snapped at one guy who was being a jerk—not so much "unprofessional" as it was just being human—and was apologizing for it long before he left the comment thread for the day. (See: comments #398, #871, #1061, probably others)
To point at one or two arguably injudicious posts and from that deduce that he should ever and always avoid any and all direct contact with fans seems a bit strong.
I have no particular objection to him saying fuck off in and of itself; he is as you say only human. But my point rather is that all individuals associated with an ongoing franchise of any sort of this magnitude should stay off the Internet and avoid these discussion forums type encounters.
As I've explained, apart from the "fuck off" being a little unprofessional (though understandable) since he's not really just a guy, he's a representative of a production team and doing that really could have (though didn't, overly) generate some bad PR, there's also the point that going on there serves him no purpose. There is no evidence that fan feedback on these forums is used in any way, and if Orci dislikes spending four years dealing its people being rude and unpleasant, it was his choice to go on the forums and it was his choice to debate. If he doesn't get that there's always going to be dicks, sad as that is, he shouldn't go on. He wouldn't lose a damn thing, and he'd deny the fan idiots ammunition.
Now, if the fan feedback on these forums was somehow essential, or there were some evidence that he takes something away from these encounters, I would say he should continue to go on at risk of making another possible PR blunder simply because anything that helps him improve his craft can only be a good thing. But of course, there is no such evidence. Unless he has specifically stated at one point, "going n fan forums helps me X". There might be some general bullshit like "keeping in touch with the fans" but honestly, that's just crap and nothing a fan says would ever measurably effect the way he writes.
I feel like I'm repeating my basic point and that this entire debate has become rather overly circular for my tastes, so that'll be the last I say on the matter.
One final note, back on the original topic before we started discussing Orci's forum going: I may not rate the new films as being good Trek, but they are in my opinion good cinema, well written enough for the vein they're in (but not perfect). If Orci can bring the same writing talent to a televised version, I say his hands should happen. I doubt it'd be the Trek I want personally, but it would be something with the Trek name and it might even be good telly, which in the long run helps the franchise survive better. Then, maybe, someone else can get to come along in a few years and either reboot Trek properly with no half arsed connection to the old series, or go back to Prime and see the 25th century (more likely the former).