A linear line on a logarithmic chart is perfectly valid. It indicates a steady rise in value. The angle of the line corresponds to the growth rate.
The thing is that a "line" on a log scale is not a line or an angle, it is a curve.
If it's linear, it has a rise over run. That angle corresponds to a specific constant growth rate.
I'm just trying to explain some math to the people that don't understand the significance of straight lines on log charts.