These things should not be allowed.
We ignore them all day long, none of our leaders actually seize the problem. That's already a shame.
But... putting spikes or other inventive stuff to just not let them sleep in places not too exposed to the wind and passersby, that's just outrageous.
You can sign here if you agree: https://www.change.org/p/anne-hidalgo-et-si-on-interdisait-le-mobilier-urbain-anti-sdf-et-inhumain-%C3%A0-paris