(disclaimer: Amazon employee)
I've made the same observation as you, but I think there are other factors at play. It seems that Amazon has become the new "cool" company to hate, just like Microsoft was a few years ago. I've personally heard a mix of positive and negative stories from all the big 3, but Amazon seems to be the only one that makes headlines.
I'm not trying to say that Amazon is perfect, or even better than Microsoft or Google, I'm just saying that maybe it is better to trust the opinions you hear from people you know rather than what makes the front page of HN, wherever that happens to take you.
During my Microsoft internship, I watched a male coworker verbally harass a female coworker to tears while she was giving a presentation and no one batted an eye. A friend told me to come check out Amazon, and I've never looked back. I would never go back to Microsoft, but I don't fault people for going there because I know that it is a huge company and that my experience isn't representative of the whole.