If you re-read the actual posting, I never specifically came out against one particular car/truck...just said unibody.
As for why, it's fairly simple. Take a look at where a hitch is bolted up on a frame car. Then, take a look at the metal, the thickness, etc where a hitch would connect to a simple unibody vehicle. In addition, a lot "traditional" unibody cars are front wheel drive. Most of those are not up to the task. For example, the Honda Accord V6. Great passenger car, but tow a 19' Bambi? I don't think so. Not designed for it. Another example, there are clowns out there who try to tow and or do move a 34' Classic with a Dodge Intrepid. Smart? Very much no! Does it move it? Sure? The stresses of towning on most unibody vehicles simply aren't engineered for higher loads. Transmissions, axleshafts, weight distribution, let alone the base unibody construction, all lead to what I consider unsuitable vehicles. Do some do it and not have a problem? I'm sure there are folks out there. There are also, even on this forum, stories and pictures of folks not doing the right thing and the results have been less than optimal. To me, it makes little sense to spend tens of thousand of dollars on an RV, and skimping on the tow vehicle. Do these statements I make blindly blanket every situation? Nope, but a good majority, it does apply. Don't beleive me? Ask any person out there that rolled their coach (they are on this forum) and said the same things...it works, what's the problem?
That is why I would never tow with a simple unibody if I had more than a 16' unit weighing more than 3000lbs...but again, to each their own.