People knock it because it's popular and well-established in the UK hi-fi fraternity and they get to score anti-hero brownie points if they can kick against the establishment, without all the general nastiness of going on a march or getting arrested. It's like a small army of ageing, sweaty, morbidly obese James Dean wannabes in ill-fitting sweatshirts pontificating over something that real people (who would never go near these people IRL) dare to enjoy a lot.
There are also those with the curious patient memory of the celibate, who recall events from the 1980s, when Linn and Naim held the UK hi-fi world in their thrall. In a similar vein, my grandfather was once delayed by nearly two hours once when the LNER train he was supposed to catch was cancelled, and yet he received no recompense. Fortunately, he managed to extract a lot of mileage from that tale in his dotage, because he used to tell us the same story every single time we visited him for the last ten years of his life. So, perhaps the obsession with what this company did 30 years ago is a sign of early-onset dementia.
There's absolutely nothing wrong with Naim and 99.999999% of the UK population if they only knew it existed would be delighted to own something that sounds so good, and is both designed and built in the UK (and known for being designed and built in the UK). I used Naim for years, and eventually moved on because I got itchy feet, but I still like and respect the brand, the ethos, the customer service... and would absolutely recommend it to anyone seriously interested in their music.
If I am truly honest with myself, since I moved away from Naim, I find myself listening more to the sound music makes than the music itself. There's an interrupt between the music and me that simply wasn't there when I was using Naim, so I'll probably come full circle one day. This is not unique to Naim, but Naim at its best encapsulates beautifully. Why there is some extra link to the music that is hard to attain elsewhere remains unclear, and will doubtless be dismissed as sentimental nonsense by those who think music is something to be endured between test tones. Nevertheless, my feelings on the matter stand.