The weight of the Tesla is moot. The majority of the load experienced by the pulling vehicle is in the incredible drag of the Tesla’s wheels. They’re extremely difficult to spin and this for pace far exceeds any others that would normally be encountered when pulling a traditional load.
Well, at 70 mph the load would be a lot. If the car were towed at 25 mph it wouldn't be as difficult, and I assume most EVs let you configure the regen amount. If you set it to light regen it'll be easier to tow, but charging will take longer.
Having at least some regen braking all the time seems like kind of a benefit, since there's less risk of the rear car hitting the front car if the front car stops abruptly and the driver in back doesn't step on the brakes fast enough.
I can agree though that if the EV being towed really thinks it's supposed to try to stop as hard as it can, it would take a pretty powerful engine/motor or low gearing in the lead car to drag it along.
The cool thing about EVs is that they have an instantaneous power meter in them, so there really is no need to speculate.
The following numbers roughly correspond to my 2017 Model S: At 30mph the car consumes approximately 200Wh/mi (6kW or 8hp) and at 70mph approximately 300Wh/mi (21kW / 28hp). This is the power required to maintain these velocities against all external factors, and therefore is exactly equal to the power required to tow the vehicle at these speeds.
If you have regen set to normal, the car will supply up to 50kW / 67hp through regen. TBH I don't know exactly what the minimum speed to achieve full 50kW is, but I am reasonably confident that the car will do it at 30mph since the tires have more than 10 times the required grip to do it.
Towing at 30mph = 56kW / 75hp, 89% charging efficiency, equivalent to a ~2000lb trailer
Towing at 70mph = 71kW / 95hp, 70% charging efficiency, equivalent to a ~2500lb trailer
The trailer weight estimates are roughly basaed average of engine power / towing capacity figures for medium duty pickups. The tow vehicle to do this safely in my estimation should have a 250hp power plant or larger.
The biggest flaw with the linked article is that it's not necessary to go 70mph to achieve the maximum charge rate from regen, and indeed it is less efficient to do so.