If your motivations are so altruistic and unbiased, then how about these alternate ways to benefit society as a whole?
Tobacco causes a huge negative effect on society...so, illegal.
Alcohol use is another, so that should be illegal.
Car related accidents is another large one, though, to fix this is a little complicated. As it is, we have spent approximately
$14.5 billion on the War on Drugs this year. That same amount of money could go to researching autonomous technologies and save over 30,000 lives a year, altruistically, i don't see how you could say no.
The #1 most used weapon in violent crimes is a baseball bat. Since life outweighs sport (as seen in your methodology towards gun control), we need serious restrictions on baseball bat ownership, yes?
Unintentional poisoning, we need to put serious restrictions and regulations on chemicals caps and buying (like how we do with Sudafed).
Medical Errors, we need to invest in robotic surgical doctors (which already exist), and can cut down on doctor errors.
And finally, unintentional injuries. I think we need to stop constructing buildings over three stories with windows that open, or access to roofs, or and cliff like access. All construction needs to be on a maximum or a 3% gradient, and all individuals need to wear protective gear. Since people shouldn't have the choice to do with their own body as they see fit. It's up to us to make sure we have their best interest in mind, amirite?
Also, on a side note, since you're playing up the altruistic approach of having only society's well-being in mind (which i might add is the philosopy and moralistic approach of most atheists (secular humanism), where to decide if something should be legal or illegal, you weigh the effects on society, both positively and adversely. If something is neutral, it should be legal, since it doesn't harm society).
Using your enlightened position of secular humanism on these points of interest, extend it to gay marriage, where there are no negative repercussions and many positive. You can't use moralistic approaches as they suit you. Or as better said, you can't take a preconceived stance and opinion and find the relativistic moral approach to support your bias without being a total and complete hypocrite. So if you wish to extend this moral philosophy to these issues, shouldn't you extend them to all issues, regardless of their significance in your religious dogma?
EDIT: On a side note,
cannabis has thousands of notable industrial uses that are absolutely beneficial to society like strengthening concrete (so that it withstands natural disasters and saves lives), ropes (which don't fray and snap, killing workers), textiles (which are more durable and cut down the cost of living), nutritious oils (that help give beneficial nutrients to the body), bioplastics (that are stronger than oil-based, and are good for the environment, and are renewable), biofuels (obviously good), paper (which cuts down on the harmful chemicals that are used for wood pulp paper), water filtration (cheap, efficient ways to purify and filter water and remove bio-chemical and excrement waste)...