The purpose of ordinary bicycle is both transportation and exercise. You can't just dismiss benefits of the other choice because your choice does not have them. We are comparing ordinary vs. electrical bike, with all benefits and drawbacks.

The analysis in the paper is flawed right from the start. For regular overweight people, which is the majority of people in U.S. and some other countries, unless getting to high speeds and high heart bpms, a little increase in energy expenditure in moving the bicycle does not increase food consumption in the linear way the paper assumes. The food is gonna be consumed anyway.

And even disregarding that, there are more important considerations here than alleged increase CO2 production, which is laughably negligible in comparison to car, plane and ship transportation. Ordinary bicycle has lower price, better health effects, lower environmental cost of manufacturing/disposing of batteries.