I think the difference here is that in this case, there is a tangible record of what was said outside of work, rather than a story about how someone said something outside of work. I'm sure there are countless examples of employees wishing that whatever their crazy coworker said after work was recorded or written down somewhere so they could report it, but that wasn't the case until social media came along and gave everyone a chance to post things online. In the example, Frank probably wouldn't have kept a written record of his opinions precisely because he knew it'd probably get him in trouble if anyone else found it.

This doesn't really answer your question of "why does it matter," but I bet that if some of the crazy individuals you worked with had posted their opinions somewhere that people could see them, they would have been fired too.