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 https://goo.gl/uRrY78: 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.