When someone says “just sayin”, to me it sounds like they are trying to make sure you know that they are trying to attack you.
Reminds me of the time when a friend of mine apologized for a comment she had made to me earlier in the day. I hadn’t realized she had meant to offend me, and she knew that I hadn’t realized it, and apparently this really bothered her so by apologizing she had the opportunity to explain to me how what she had said had been meant to put me down (apparently she had been upset by something I had said that I hadn’t realized was upsetting to her and she wanted to pay me back by putting me down but then was annoyed that I didn’t chap that it was a put-down.). Then when she realized I still wasn’t that offended even after she explained, she kept going on about how nasty her comment was (she sounded very proud of herself for coming up with the comment and she really wanted to make sure I realized how insulting it was).