Ben, Sorry to hear of your negative experiences. Unfortunately some people are so small-minded that they have to attack anything that they don't understand.
While I have never had someone directly disrespect me while driving or riding a modded vehicle I have been viciously attacked on other forums when I have posted info or pix of mods I have done to my car or my motorcycles. I have learned to expect this response from non-hypermiliers and so I don't post much more about my hypermiling efforts on those forums unless someone asks about fuel economy. As others have stated, you do have to develop a thick skin, its just human nature.
As I have progressed with hypermiling, I now run only stealth mods on my car ( grille block, high tire pressure, lip spoiler, HAI , etc.) . Now I focus most of my modding efforts to my motorcycles with radical streamling ( long pointed tail, taller longer windscreen, faired wheels, etc.) and people definitely notice. WHile riding on the freeway I often have cars run alongside me so that they take pictures of the " Batcycle" . My motorcycle gets more attention than a Ferrari but people seem to like it. Strangers often ask me about the mods while I am refueling or using the bike on errands and seem very interested. One of the things I do is keep a magnetic sign with my best Mpg posted so that people will understand why the racy -looking motorcycle is cruising along at the speed limit. You might try that on the rear windows of your car.
One thing that I have found very helpful is to meet with other hypermilers and share experiences. I have made some great friends who totally understand my motivation. Absent of direct contact, I have made other friends on this and other fuel economy forums. Its great to find other people who are passionate about making a difference.
Hang in there buddy, we feel your pain. That which does not destroy us just makes us stronger.
best wishes , L&S