For the whole, second hand smoke bullstuff, it is almost impossible to get any high, at all, from smoke 20 feet away. And again, you have a MUCH higher chance of being hurt by tobacco second hand smoke than marijuana. And it's not to say that with the passing of marijuana legalization that there wouldn't be laws against where you are allowed to smoke, and having 'no smoke' policies. It can and probably would be treated just like tobacco.
My argument with the second hand smoke bit is not that you worry about getting high, it's that you worry about the damage it does to you.
There may be numerous tests claiming that smoking cannabis doesn't do as much (some say no damage) to your lungs/throat/mouth as tobacco does.
But street cannabis is most commonly mixed with tobacco. Simply because it is cheaper. Cannabis isn't ridiculously cheap to produce, so when someone goes about selling it, they want the most out of what they sell.
So, just as with other drugs, they split the cannabis with tobacco, so that they give you the same amount of product, but less cannabis in total, letting them sell less cannabis to more people for more money.
Luckily cannabis mixed with tobacco isn't as bad for your health, or as ridiculously dangerous as other drugs, such as when cocaine gets mixed with a number of subtances to give an illusion of there being a significant amount of cocaine. In those cases, people often die from snorting poisonous substances. And the deaths can be quite brutal.
But that doesn't mean cannabis+tobacco is any good. It's well known that tobacco smoke is a carcinogen. I don't want to be breathing that in, and neither should you.
And if you honestly believe that most cannabis that people buy out on the streets is pure cannabis, then you're deluded in that. Any actual drug dealer knows how to make the most money out of their product, and making the most money almost always includes adding poisonous or harmful substances to the drugs.
Also, if cannabis were legalised, then there would be restrictions on it, as well as guidelines for it's production.
It wouldn't be smuggled in from the border, or grown in people's attics anymore. That would still be illegal.
It would have to be properly produced and regulated cannabis that follows proper rules in it's production, packaging and selling.
So, for starters, you're not going to have government regulated cannabis being distributed being mixed with tobacco. Because people will be outraged that tobacco is being mixed with it. People know that tobacco is dangerous and harmful, both to you and people around you. So the government could not legally produce cannabis mixed with tobacco. Instead they would have to sell pure cannabis.
So, what this means is that companies who produce cannabis will have to have full cannabis farms (which are regulated), and they have to sell the entirety of the cannabis. They can't mix it with tobacco. So, for you to get the same amount in your joint, they put in more cannabis.
Them putting in more cannabis means they need more farms. More farms are more expensive. There's more cost for the government in regulating these farms. The price of cannabis would increase. It's not going to be cheap to get your legal cannabis.
It would cost more than it ever did before. Because now when you pay for the cannabis, you're not just paying the dealer for his services and the grower/supplier for his job in producing it, you're now paying a company for the cost of growing the cannabis, the cost of it all being held to regulations, the cost of the packaging, the cost of transport and distribution, the price that shopowners put on it to make a profit, the cost of advertising (If there are adverts) and the tax that would definitely be put on cannabis.
So, now, are you going to go and buy these much more expensive joints of cannabis in a carton, or are you going to go back to the dealers who have been getting unregulated and cheap(er) cannabis from overseas and from illegal farms, for much less.
Legalising it isn't going to get rid of unregulated and illegal cannabis.
And the government is not going to legalise cannabis and then not regulate it. That defeats the point of legalising it in the first place.
And even if you don't agree with the above, and you only ever smoke pure cannabis, then there is still the problem of second hand smoke.
I don't care if it doesn't harm me. I don't want to have to breathe in smoke, of any kind. I don't want to walk past someone, breathe in the smoke from their cigarette, or their joint, and end up coughing. It's an invasive thing and it's not nice.
You wouldn't let someone slap you in the face once a day. That's not going to cause you any proper harm. It's not going to give you a disease or break parts of your body. It doesn't mean you're happy to let people slap you though.