Absolutely agree. Co-workers are dangerous friends unless you know them very well. Express a politically incorrect opinion and you can find yourself before an HR Star Chamber or worse.
About a year ago, I started a second job to pay the bills. Unfortunately, I fell asleep at my main job. I don’t believe that it had anything to do with my other job. I didn’t fall asleep, per se. I passed out without warning. It was probably low blood sugar or something. However, my co-worker piped up and told my boss that I was working a second job.
I had a lot of explaining because of my coworker and I learned to keep my mouth shut in regards to my life outside the work place. I still resent him to this day, because he nearly cost me everything for no reason that concerned him.