I would be willing to bet your colleagues at work would find it annoying and impolite too.
Perhaps it is a difference in 'climate' between working in a science based industry where we often get challenged on our data versus software development industry. Maybe I've spent too long in academia where 'citation needed' is an indicator of interest in my topic and considered a good thing.
I was not aware that "citation needed" is considered impolite. It is something I use at work a lot when interacting with colleagues. My apologies, I'll refrain from that in future.