Petrochemical manufacture and the millions of products that contain them all rely on the oil industry, not because petrochemicals are a "cheap byproduct", but because they can't be sourced or synthesized from "renewable sources". Cannabis products can be substituted for some, but not all the by-products oil, so oil rigs, Derricks or other forms of oil procurement would still be needed. Therefore your argument is based on a fallacy. Again, there are exceptions to your argument; A volcano can cause Acid rain. Ending Cannabis prohibition will not end Volcanoes, so your post contains more fallacies. There are many good reasons to end Cannabis prohibition, using a sensationalist topic (Oil rig tragedies) will only persuade ignorant people (or whatever type of people it is that buy tabloids)
I dont know where u get your info but u best be checking it, because everything that petro chemicals currently makes CAN be 100% replaces with hemp and at one time was. From 70-90-% of all rope, twine, and cordage was made from hemp until 1937. It was then replaced mostly by petrochemical fibers woned principally by DuPont. Petro chemicals came from I.G. Farben which Hitler owned during WW1 and was the leading developer on petrochemicals, and was at the time the world 4th largest company, behind General Motors, U.S. Steel, and Standard Oil. (wikipedia I.G. Farbe,). At the end of the war germany had to surrender their patents in reparation paments to America. Also some 30% of Hitlers I.G. Farben was owned and financed by America's DuPont. Also "congress and the treasury department were assured through secret testimony given by DuPont in 1935-37 directly to Heman Oliphant, chief counsel for the treasury dept. that hempseed oil could be replaced with synthetic petrochemical oils made principally by government owned DuPont." (The Emperor Wears No Clothes) That is what the govrnment has tried to brain wash us into believing my man but its not true. we CAN be totally independant of oil. If you have never heard of the book "The Emperor Wears No Clothes" you need to research it and buy it and give it to as many people as you know to read it.