Pick a business, any business, and I can promise this will be true: There are those who know what they're doing, and those who only think they know. The same is true in writing and editing.
I wrote once about giving a critique some thought before dismissing it entirely, there were plenty of folks who agreed with me only up to a certain point. Caution flags always rise in an author's mind when someone is suggesting they listen to anyone other than their own gut pertaining to their work. Despite what I said in the post, I agree with them. Particularly when they know the difference between critics who know, and critics who only think they do.
There are writers who are just learning their craft, and part of learning is critiquing other works. Many writing forums contain these folks, and that's great. These forums are the perfect place to sharpen your writing tools. But experienced authors can recognize the difference between experienced critics and those who are learning. One caveat about disregarding inexperienced critics: they're readers. If there's something in your work that hits them as "off," maybe it is. They may not know how to express it, but it doesn't hurt for you to look beyond their remarks to see what it was that made them comment in the first place.
There are critics who are sticklers for the rules and don't allow an ounce of artistic license. You know your work. You're not a big fan of flowery prose, and you haven't used it. But this one place calls for it--makes the piece more touching, more powerful. Your critic slaps "Purple!" across the page and red-lines the entire passage. Any amended version you write comes out stilted and formal, and your preference is the original. If it's purple, so be it. Your choice, and in my mind, the right one.
Or in the case of POV preference: if your genre is one that allows a distant third person POV--political/international thrillers, espionage, certain mystery/police procedurals, among others--stick to your guns. Just make sure you're writing your POV correctly and not head-hopping.
Finally, there's the stagnant critique group: those who have been together forever and are all on the same level of expertise. I have a friend in one of these groups. She'd listened to their advice, taken much of it, and was still getting zapped with rejection letters. After giving it a bit of thought, she realized they'd been working together for six years, yet not a one of them had published anything. If anyone in the group was serious about getting published, surely someone should've been. Sounded to me like the same tired advice was being passed around ad nauseum, and no one was growing from it.
So, these are a few examples of when to pick and choose who to listen to. But how do you know when you've chosen the right criticism to ignore or accept? How can you prevent yourself from taking everyone's advice and losing your voice in the process?
This is where personal accountability comes in. You can't know if you don't know. Study. Study the how-to books. Study other successful authors. Even study the boring grammar and style books. If you don't know any more than your critters do, then the blind will lead the blind until everyone bumps into a dead end.
This may sound contradictory: If you study, why would you need a critique? Because authors are notoriously blind to their own work. But if you study and you submit your work to be critiqued, you'll recognize good advice when you see it. May sting a little bit, may make you want to shower in a Bactine spray, but in the end, you'll know that the advice is at least worth a try.