The rules are the rules, pointless wittering about whether you think they are right or not, is not an excuse to break them. BA say no vaping on-board or in the lounge, so no vaping - pretty simple. Don't like it, don't fly. I'm sure you'll survive with a nicotine patch or other approved in-flight option. Expect next those people who vape marijuana to cry violation of their rights in that they should be able to do that on-board too (regardless of the rules).