No matter how much you may agree or disagree with any critique of your work, NEVER dismiss it out-of-hand. There can be great value in a critique that you don't agree with, as long as the critique points out places that may need improvement. There's always the possibility that those critiques will turn out to be wrong, but in the editing stages of your work, it never hurts to take a second look.
With that said, don't go around making EVERY change suggested by the people who critique your work. Listen to their advice, then make your OWN decision! It's YOUR book, after all.
I recently received the critiques that I paid for with the RMFW contest. I didn't score as well as I'd hoped, but without a point of reference, I can safely say that my scores were not at ALL disappointing. One of the judges gave solid critiques, noting areas of the manuscript that needed work or polish. They didn't make any assumptions about the state of the book or suggest that I COMPLETELY rework the entire thing. While some of their suggestions differ from the notes I've gotten from my critique group and beta readers, on the whole, they're very helpful.
The other judge barely marked up the manuscript. Instead, they recommended making one of the secondary characters my protagonist. This assumes that this book is still in its early stages. And because this book is basically done and in first person POV, it's also a recommendation to write a completely different book. Rather than work with the one I've written.
BUT I don't think they wasted their time or mine. Sure, they could've been more helpful and given critiques rather than "this is lame, unbelievable, I'm walking away now" comments, (stuff I WOULD have listened to if it didn't directly contradict 10 other readers who dove into the story head-first and loved it, even while they "tore it to pieces" to help me make it better). It's still useful, though, because it makes me look at my writing as a whole. It makes me evaluate everything I've learned, read, and accomplished in this manuscript.
The only other note I can give to you, my readers, is that when you're giving critiques, be helpful. Don't be afraid to say the tough stuff (like "I don't know if this is working" or "this is difficult to believe"), but make sure that it's said in a way that helps the writer. Use examples of "why it doesn't work" that are relevant to the story itself. If a story takes place in the distant future and an evil person wants to do an evil act, don't say "this country wouldn't let that happen because in 1986 they passed a law that banned that action."
Laws change, nations change, governments change, and evil people will ALWAYS do evil things and create conflict in the universe, even if their governments passed laws banning those acts two or three hundred years ago.