No, I don't think cyclists are significantly "more in tune with their food intake" - I would wager 95% of them have never considered how their food consumption affects the environment.  Nor do I think car drivers are likely to be eating more of it - cyclists are burning a lot more energy, and will be hungry more often.

You used the factor of 3 calories for every calorie produced - but if you read the whole quote, you'll note it says that study only considered one aspect of food production, and other studies say 7-10 for the total number.  This, of course, makes the cyclist a third as efficient, rather than even with the gas-guzzler.

Sure, there's a possibility their food was grown sustainably and with minimal energy consumption.  You'll note I even mentioned this in my post.  But, it's unlikely.  Most people don't buy only local foods, and even many local foods, especially in other areas of the country where organic and sustainable agriculture isn't practiced, use quite a bit of energy to produce.

I'm not sure what kind of meat you think uses less energy than vegetables, unless you're considering hunting.  All mass-produced meat, even the local humboldt grassfed, uses a large amount of energy - and hunting has environmental concerns too.  While local natural meat is obviously better, it's still not as good as local vegetables.

Making a motorized bicycle does take additional energy - so does making the tractors, trucks, etc involved in farming.  Motorized bicycles are probably kept longer and resold or repaired when a regular bike might be scrapped, as they're considered less-disposable than a regular bicycle, negating part or all of this factor.

Maintaining a car does, indeed, use far more petrochemicals than the occasional spray of chain lube and new tires for a bicycle - but we're comparing a regular bicycle to a motorized bicycle, not a car.

Cars don't kill things, bad drivers kill things.  There's tons of bad cyclists too, they just aren't sitting on enough mass to do as much damage.  But, we're comparing to a motorized bicycle or light motorcycle, which has only slightly more mass than a regular bicycle - and, as you pointed out, a much lower speed than a determined cyclist, making it less likely to kill things.

Just the petroleum used to produce the fertilizers for an acre of grain is similar to the asphalt contained in an acre of blacktop.  For example, ammonium nitrate is the most-used fertilizer, which is produced from natural gas, with a huge amount of energy put into the process. Ammonium nitrate, on commercial farms, is used from 100-1000 pounds per acre, and uses several times more than its weight as a feedstock and energy supply to create.  Many other fertilizers are used, and some need more energy, such as urea needing ~10% more energy for the same amount.  Asphalt is 6% bitumen, and is 75 pounds per square yard at 1" depth. An acre of blacktop, 2" thick, contains ~43,000 pounds of bitumen - roughly the same as needed to produce the fertilizers for an acre of farmland over the life of the blacktop.  You're right - I didn't calculate this before.  But, now I have, and you can see the results yourself.

As the motor is situated behind the posterior of the rider, I suspect its aerodynamic properties are relatively good, as the air stream is already split.  It's certainly more aerodynamic than a rack or basket on the back of the bicycle.

Cyclists indirectly create pollution and noise.  Much of the billions of pounds of fertilizer used by commercial farms runs off into rivers, causing algal blooms and other problems.  The process to produce ammonium nitrate produces huge amounts of CO2, from all the natural gas used as a feedstock just for its hydrogen.  Most of the energy needed to produce the food comes from pollution-generating sources.  All of these activities produce noise as well.  Or, for more minor noise sources, cyclists cause automobiles to produce noise, from the horns honking every time one of them thinks stop signs don't apply to them and the sounds from the obnoxious rumble strips they insist freeways should have, and directly from cyclists yelling "poser" at more-efficient passerbys.

Of course, I agree with you on some points.  Improving agricultural practices is a very good idea, and would make cycling less of a bad idea.  And friction drive is, and always has been, idiotic.  The guy posting these is a spammer, trying to make a buck off innocent people. But "ride lots" isn't some miracle solution, and for the average person, doing that riding with a motorized bicycle won't be any worse than pedaling.