Many Harley baggers have the same tire width and cross section ratio as TWs.
Harleys are factory tuned way too lean, just like TWs.
Harleys and TWs both are based on antiquated engine architecture.
In their day, Harleys were the fastest things on wheels. Therefore, many crooks acquired Harleys for get-away vehicles.
Harleys got a bad rap with the portrayal of criminal elements riding them in movies of the '50s and '60s, furthering the criminal biker image.
In the '70s Harleys got a bad rap under AMF ownership, which stressed profit too highly, restricted engineering to remain competitive performance-wise with the Japanese marques, and allowed quality to slip.
Middle-aged yuppies of the '80s, most having never really done much more with their lives than sit in a cubicle 8 hours a day and flopped in front of a TV 8 hours a night longed for a way to grow testicles. They were a ripe market for the "Harley lifestyle" marketing campaign, a brilliant business move on Harley's part to advertise and sell a sense of having testicles for the small price of a Harley motorcycle--no other would do--at cheaper rates than a lifetime of psychological counseling, a price commensurate for the other alternative to suffering such a dreary life: a funeral.
It is here that the majority of Harley and TW riders generally separate. Most (estimating 85-90%) Harley riders haven't a clue about functionality--they are either projecting an image they misunderstand as having testicles or are merely lemmings chasing after the group like the littlest kid in the neighborhood's plaintiff "Wait for me! Wait for me!"
I've found that a few (estimating 9-14%) Harley riders actually enjoy their Harleys. They see the good-natured shake at idle as one would his best friend's tendency to pick his nose--a point of contention that really has no influence on functionality. Their bodies are generally shaped to fit Harley ergonomics. They ride at moderate speeds, are courteous to others on the highway, operate their Harleys within the limited (compared to more modern designs) performance parameters of their antiquated design features, and enjoy themselves tremendously. No different than one who drives a 1928 Model A or a CB550 these days. These are those few Harley riders who ride with a big shit-eating grin plastered across their faces, those whose Harleys are well-maintained at home, who rarely have a breakdown, and who generally rack up lots of miles. They tend to avoid events like Sturgis and R. O. T. and Daytona Bike Week. Engines tend to be stock with minor mods and tuning rather than major performance builds. Modifications tend to lean towards function instead of bling. Most have a relatively quiet exhaust that sounds really good without the headache-inducing pounding of straight pipes. They are more likely to wear a 3/4 or full face helmet instead of a beanie, and tend towards armored gear rather than branded fashion leather. They usually pay cash for their bikes, too. These are the Harley riders who would likely choose a TW for a dualsport bike. Actually, they choose a TW for the exact same reasons they choose a Harley--the friendly power delivery, the inherent durability of low-stressed components when properly maintained, readily available parts enhanced with backwards compatibility over decades of production, and most of all, an honest personality with no surprises. These riders are usually seen riding alone or with a small group of other cruiser/bagger bikes, and those probably own TWs, too. They know exactly why a dog sticks his head out of a car window. they are easy to spot at a BBQ joint jammed with motorcyclists on a holdiay weekend--they are the small, quiet group off to the side.
Then there are the 1%ers from which the sterotype is drawn. Yes, there are a few, probably way below 1% due to the huge influx of testiclelesses buying into the "lifestyle", but most will only be seen riding with their brothers to a funeral or such. Their, uh, business interests make it unsafe for them to ride alone.