The problem with e-cigs is they are a public health threat and worse they entice children to begin smoking so they have life long customers who are addicted to a dangerous substance and expensive habit.
Plain old regular cigarettes were and are on their way out. They are nowhere near as popular as they once were which is why e-cigarettes became the must-have alternative for the tobacco industry. Once they saw they could hook kids with the fruity flavors, the "cool" alternative look of "safe" smoking they knew it was going to stave off their demise.
Marijuana? It is not addictive and taking the generous stance that it is, not nearly as much as tobacco and the dozens of chemicals in it. Or e-cigarettes with it's own plethora of chemicals.
Nicotine just plain needs to be banned. Caffiene? Yes, it's addictive but I don't know of anyone who takes it and gets cancer as a result. Or COPD, or any other serious side effects.
Don't try pulling what about-ism on ****ing nicotine. There is only one other substance more dangerous than it that's legal and sugar is not being banned any time soon.