No, I can't believe that either.
Baby On Board stickers may (depending on your individual pov) be smug, annoying, pointless or whatever; but how you can compare them to these nasty stickers is completely beyond me.
Also, as for saying you shouldn't be driving that close if you can read the small writing - most vehicles spend most of their time parked and not moving at all. You can safely get within an inch away from a stationary vehicle in Asda car park.
Children who are discovering and getting a handle on the world of reading are often naturally very drawn to any words they see out and about, keen to read what they say.
Even if you don't subscribe to the 'it takes a village to raise a child' viewpoint, I personally find it abusive to deliberately display signs, pictures and messages like this in a public place (which is what the outside of a van is), where you know very well that loads of children will see them.
By no means just children, either; I can't think there are many people at all who would be delighted to see what is effectively a public noticeboard that resembles the inside of a toilet door in a seedy pub. The driver is already coming from a point of great privilege if this stuff is just a laugh/turn-on for him - it will be highly inappropriate, threatening and/or triggering to plenty of others who can't easily avoid it.