Is a juice detox safe?

Depends... Dr. Cole raises an important point. If you are using juicing in addition to a regular healthy diet to detox, then it is safe longterm. If you are doing a juice detox fast, then it can be problematic. The liver needs a tremendous amount of energy to work efficiently. Fasting longer than 24 hours can influence the metabolism of the liver.
Detox is a 24/7 job. handled by multiple tissues & organs of body. Food processors perform focus group studies of formulas, sales & packaging options to see what sells best, thus Yes, addictive to ? sales. Efficacy & safety require expensive double blind placebo controlled prospective clinical trials for any scientific validity (thus Not Done). See OTC industry commercial exempt them.
Depends... ...On how long you do it for, and if you're using any other supplements. The major problem with longer term use of a juice fast (more than a day or two) is muscle wasting due to a very low protein intake. Any detox can be difficult to handle, and you should be in pretty good health to begin with or do the detox under a doctor's guidance.