There is no provable coloration that a drugs use will increase just because it becomes legal. (there is week evidence to support the opposite)
Lets take Prohibition for example: (source) While alcohol consumption temporarily decreased, in the early 20's by prohibitions end, Alcohol consumption was up 60-70%. It allowed 'organized crime' to create a toe hold, they still have. (mainly through other prohibitions) And allowed for countless Americans to be killed or injured by tainted hooch. (The lesson from history is NOTHING GOOD CAME FROM PROHIBITION)
There are lots of things that are highly addictive. Drugs, Money, Power, Sex, Food, Music, Thrill Seeking et all. Most drugs are probably not nearly as dangerous or addictive as you believe them to be, and the ones that are, would likely not be used nearly as often, if a less dangerous, less expensive form of another drug were more readily available.
I don't want people around me thinking it's okay to get high and start having hallucinations and getting violent around me.
I don't know of any drug that causes those symptoms, PCP aside. There is nothing the government can to but 'rush to your aid' should a sober person decide to 'get violent round you' and thats just as (if not more) likely than encountering someone on PCP.
And if weed were cheep/legal, you would not have to worry about that at all, Because the stoners would just sit around the house and play video game, LIKE THEY DO NOW.