With all due respect
about 1 in 3 children will try burning tobacco
about 1 in 4 will become habitual users
about 1 in 6 children will continue doing so until they are dead *

This is the current status quo, and this accepted as a great improvement.

E-cigarettes represent that safety helmet. If your kid becomes an adult, and smokes, this is the alternative since it is the status quo to continue smoking until your dead.

I don't know a single parent who wouldn't accept e-cigarettes as a fallback position if they fail at teaching tobacco abstinence when their child becomes an adult.

* http://www.tobaccofreekids.org/research/factsheets/pdf/0127.pdf