I was enthusiastically commenting on a healthy niche market and then I used a metaphor point out that it's not just a hobby or a toy that these people are working on. It's a sophisticated tool that interfaces with the outside world much like CNC, which happens to be my area of interest.
Simile: "It's like CNC for trains!"
Literal truth: "It's called DCC actually"
If your point was to add information, then there was a better way to do it.