Whether being in an unmarked vehicle or not, someone bent on doing bad is going to do it.
Vans get an undeservedly bad rap.
When the Anthrax scare was going on years ago up and down the East Coast, it was reported to have likely been a white van. We know now it was an employee of the Defense Dept, if I recall correctly. I'll bet he drove a Toyota sedan or similar. What he drove actually had nothing at all to do with the crime, but a van was immediately blamed.
When the DC Sniper still ran rampant, the media said it was a white van or box truck, largely based on a single witness report at one of the various shootings. It was repeated and reported widely. One commentator said it had already been ditched in a nearby lake. I remember fueling up 600 miles or so from DC and the general public all over the US was worked up enough they eyed me, in my white van 600 miles from DC, suspiciously. The DC Sniper vehicle of choice ended up being a 1990 Chevy Caprice, still very much dry.
I get my hackles up when people automatically connect rape or abduction or other crime with white vans.
When a friend, acquaintance, or family makes any kind of crack like "your rapist van" or "your child molester van" I let them know it is not appropriate, and is based largely on media fed bull playing off long-held unfair misconceptions.
They typically say "I'm just kidding!" to which I always reply in a calm tone "Well, if you can explain what you find the least bit humorous about rape, molestation, or abuse of any kind, I will pretend to laugh, okay?"
White vans are simply one of the most plentiful vehicles out there and make an easy target for blame. It actually behooves us--those of us who employ vans, white, marked or unmarked, or otherwise in our daily work--to actively try to dispel the misconceptions. Keep your vehicle looking fresh, be professional and polite, don't lay waste to where you park, and just generally make a positive impression on those around you.
It should not matter in the least if a van is unmarked or not to be able to park anywhere. That simply should have nothing to do with it. I see more rat cars and rat pick-ups with shady characters in parking spots than I ever do vans, especially at truck-stops. I also see more lettered white vans that look trashy than I do unmarked white vans.