I think in some cases it's not the style of bike so much but the image the riders of those bikes have created. I'm guilty of it myself, but hate is not the proper word. When I see 3 sport bikes doing wheelies and stoppies and constantly changing lanes on a busy highway the mind registers sportbikes = asshats.
When I see 6-8-10-20 Harleys in a serpentine line running red lights and doing 30 on a 45 mph road with open exhausts and the "required" rev the crap out of it at every stop my mind registers Harleys = asshats.
I can look at both styles of bikes in a showroom or a parking lot and admire them for what they are....
Add an asshat and put them on the street and the broad brush comes into play, even though I know better.