The current collaboration playlist allows anyone to delete the whole list of songs, or secretly delete individual songs one by one. Which makes the collaboration feature pretty useless.
To prevent trolls from destroying a playlist, my suggestion is to add special privileges to the owner of the collaboration playlist. So anyone can SUGGEST songs to add or delete, in the playlist. It then pops up a yes/or no option to the owner of the playlist.
Please bear in mind that the Community is not an official Spotify support service. It's a place where we all help each other, whether we work for Spotify or not. So please use your discretion when using the forum.