* "Unpleasant design" is different because it aims to exert social control in public spaces
* "Unpleasant design" is different because it is intended to create a hostile atmosphere - it increases unpleasantness rather than pleasantness
I don't really agree with either claim.
All design of public spaces is intended to exert some form of social control. Creating a manicured park with flower beds, comfortable benches and beautiful splashing fountains is intended to exert social control by encouraging people to congregate and spend time in the park. In fact, any good designer attempts to exert control by encouraging certain behaviour patterns over other behaviour patterns.
"Unpleasant design" is not intended to increase unpleasantness. Some groups perceive people sleeping on benches or congregating ("loitering") as unpleasant, just as other groups find preventing people from sleeping on benches or congregating to be unpleasant.
I'm not defending the particular examples of design referenced in the article. I'm not saying it's a great idea to make benches you can't lie down on. But I don't agree it makes sense as a distinct category of design. It's just design that tends to favour groups higher in the socio-economic hierarchy at the expense of groups lower in the socio-economic hierarchy. This may be a very bad thing, but I don't think it's a different type of design.