You could look at it as trying to get them blocked by search engines. Can you detect when they're proxying a search bot as opposed to a user? As for punish, you don't have to make it eye-bleach, just enough to make it firmly NSFW so nobody can get any business value from it, or even use it safely at work.
A little soft NSFW would also greatly accelerate them being added to a block list, especially if you were to submit their site to the blocklists as soon as you started including it. You can include literally anything that won't get you arrested. Terrorist manifestos, the anarchists cookbook, insane hentai porn... Use all those block categories - gore/extreme, terrorist, adult, etc.
A little soft NSFW would also greatly accelerate them being added to a block list, especially if you were to submit their site to the blocklists as soon as you started including it. You can include literally anything that won't get you arrested. Terrorist manifestos, the anarchists cookbook, insane hentai porn... Use all those block categories - gore/extreme, terrorist, adult, etc.