He says drug addicts should be helped with their addictions, which tax income from the sale of cannabis could and should be used for, rather than be made criminals.
"The anti-drug people will say lock them up in prison and let them go cold turkey.
"What does that say to my nephew? How is that going to erase years of violence and the pain that goes with it."
Another aspect that has influenced his opinion is the black market of drugs which has given gangs an income.
Gangs selling weed and other drugs have "built themselves empires", fight and defend their territory, and recruit young people with the promise of easy money, Barker said.
If drugs are available, he believes the state should regulate them and cut the gangs out, "chopping out their money supply".
For undecided voters, he says if they can find one concrete thing which has worked in the current regime to vote to stick with it.
But they won't, he says, in which case they should vote for change.
His view comes from his observations over the past 50 years of a failed system where nothing has worked and the drug problem has only increased.
"Doing the same thing over and over again and expecting the same result is insanity. If we want a different result, we've got to do something different.
"Try this and it fails, we've got to try something else. Let's go and work on this until we get an answer. What we are doing now is demonstrably not working."
A flaw of the proposed bill in his eyes is that "it doesn't go far enough".
"I'm voting for marijuana as a start - hopefully we'll see this works and then we move on the others."
Citing Portugal as a country which has decriminalised the use and possession of drugs, he says they pioneered the shift away from a law enforcement approach to treating drugs as a health issue.
A 'big marijuana' replacing big tobacco argument is not a certain outcome and would only happen if the regulator allowed it, he said.
There's also "no logic" to those who say the legalisation would increase drug driving, Barker said.
"I'd say that there's a lot of people who drive under the influence of marijuana today, so making it illegal, has that stopped it? No, it hasn't. Has it prevented it? No, it hasn't."
On the argument that marijuana is addictive and unhealthy, Barker says the same applies to cigarettes and alcohol and that humans are capable of all sorts of addictions, but addiction does not mean it's a crime, rather an issue people should be helped with.
