"You'll never be published." I'd expect these kind of words from a non-writer, but I'm shocked by the amount of times they commonly leave writers' mouths as well.
I've been told this because I got upset over something another writer said about me once. I've heard people told this because they couldn't handle critiques or rejections that agents or other writers gave them. I've heard people saying this when they see a writer ignore their advice and go off to do their own thing. And I've also heard people say this because the person in question had no grasp of the English language.
Writing is a learning process. We're all at various stages and levels of it, understanding concepts of some things and not others. All of us do stupid things at times and have to learn the hard way or take certain critiques wrong. I know I've ignored advice before only to have it haunt me later.
But people can only take so much growth as writers at once. The very first manuscript I wrote, someone told me was so bad, I should just trash it. It hurt and I was offended after working years upon it. They said the language was too flowery, the problems were cliche, and the characters were boring. And you know what? They were right about all of it and I wound up trashing it, but it was too much for me to take in all at once at first. I got angry at the person, who probably thought I was an idiot. I had to process it for awhile before I could improve. Growth happens in writers slowly, which is why we so often see people getting defensive about their writing. They can only take so much of the advice at once as their brains mature. Be patient with them and remember the amount of work that was put in your own error-riddled manuscript. I've had beta readers argue with my critiques and I don't usually push most issues because they don't generally argue unless I'm giving them more advice than they're ready for. I also always keep in mind that I could be wrong.
Not to mention that writers don't always have bad attitudes about it. Sometimes they receive so much advice that they wind up getting overwhelmed and getting writers block. They're not ready for all those ideas to be thrown at them at once.
That being said, it's all right to confront an author about their bad attitude or the mistakes in their writing. They'll never learn unless they are taught in some way how to do things right, but just know that even if they argue with you, get angry, or don't do as you say, it doesn't mean that they'll never be published or never wind up getting better. They're still learning and the only ones who truly never will be published are the ones who give up on their dream forever. The rest of us, with our bad attitudes and flaws, are still in the stages of learning and messing up. And also learning how to handle things with more maturity.
I've always thought good beta readers and critiquers (of queries, manuscripts, and synopses) were the ones who see your potential and not your flaws. They point out things because they know you can get better and want to see you achieve your goals. They'll never resort to telling you that you can't make it or that you are worthless as a writer.
And yes, you are welcome to point out when I do something wrong. I'd rather hear the criticisms than live in ignorance about it and make a fool of myself in front of more people. Every day I learn and am amazed at all the things I didn't know when I first started, so I'm expecting to improve a lot as an author in the future.
I just don't always expect to get critiques perfectly the first time. I've been told show, but not tell for years and I'm still learning new things about it. It's frustrating that I can't get good all at once. I just want to write the perfect manuscript and trying to do so has been giving me many headaches lately. Because I can only improve so much all at once. It takes a lot of time to be good.