As it currently stands 80% of our energy production in the United States is through fossil fuel sources (petroleum, natural gas, coal) with 8% from nuclear power and 11% from other renewable sources (U.S. Energy Information Administration). So, what is the problem with this? The problem is that petroleum, coal and natural gas are objectively poor ways to produce energy at this proportion.
Between fossil fuel producers getting $20 billion in subsidies annually (Environmental and Energy Study Institute) and the government (with their hands stuck in the pockets of oil companies) allowing them to frack and build pipelines the facade of it being cheap and reliable is going to continue. Not to mention the biggest cost (which is incalculable) to our environment and cities.
The United States must start utilizing other methods of energy production or else we are going to keep destroying our planet and be stuck with a ton of fossil fuel infrastructure when we run out within the next 70 years. Saying no to Line 3 tells Enbridge that we need to start transitioning our energy infrastructure. Tell them we need nuclear power plants, solar panels and wind turbines. All of which are underutilized and are reasonable means of energy production even in northern Minnesota. We cannot appeal to the draw of short-term economic benefits to our community that building a pipeline would bring. If we do, the economic impact of being stuck with oil infrastructure when alternatives are cheaper and better is going to hit us even worse. Let us start the transition sooner rather than later so we can catch up with the rest of the world that is already ahead of us.
I am not saying fossil fuel cannot be a part of our energy production, but it must stand the test of economic viability without being propped up by the government in order to find its appropriate role. Each method of energy production has their own flaws including renewables. A great analysis of these is given in a lecture series called "The Science of Energy: Resources and Power Explained" by Dr. Michael E. Wysession, a geophysicist at the University of Washington in St. Louis. If you care about more than what benefits this community in the long term, I encourage you to continue looking into why Line 3 is bad for Minnesota.