There was a march this weekend for exactly that in NYC.
It was rather amusing to watch people parading around arguing for being disrobed, for the street they walk on to not exist, to have no means to get to and from same, for the signs and markers used to make them to not exist and in fact to not have the free time to march at all.
Oh, and to slaughter a few billion people world-wide as well.
You see, without fossil fuels the shoes said people were wearing would not exist. Remove them now, jackass, and set your own example.
The street would not exist either; asphalt is made out of oil, so you would be walking a dirt street.
Said street would be covered in horse piss, because there are no cars, trucks and similar -- and somehow goods have to get places in quantities that a human cannot carry; ergo, you must use beasts. Fine, but said beast will piss and crap wherever it is at the time. You can capture the crap with a diaper, but not the piss. Thus you will walk in it.
You would not be there because the vehicle you used to get there would not exist. Oh, you say, we'd use electric trains and such. Fine, except without petroleum there are no insulators for the wires and thus there are no electric vehicles either. You could probably use steam without petroleum inputs (there are biological alternatives for seals and oils, for example), but what do you intend to burn to make the steam? I thought you didn't like burning things? As for the oils most of those marching have plenty; we'll use them for the source.
There would be no cellphones. Virtually every component in them requires petroleum to manufacture it. The screen, processor, battery, case, sealants, connectors, antennas and more. If you oppose "fossil fuels" take your cellphone (and computer; same issues) and throw them both in the trash immediately. In a no-fossil-fuel world they will not exist so you might as well get started now. Oh, this applies to that nice flat-screen TV you own too. Throw it out. You're not a pig and a climate-criminal, are you?
If you're a man you would have no time to march at all because without fertilizers (all you'd have to fertilize with is what comes out of the back of your horse, ox or similar) your crop yields would be a fraction of what they are now. Without fossil fuels you cannot pump anywhere near the quantity of water now consumed, nor till the land with other than said beasts and there are no pesticides. All this makes some people happy right up until they realize that now you must work said land by hand and raise small animals to survive, leaving you no time to go wave signs in a city.
If you're a woman you get to join said man in the field because you must produce too or you will starve. The only exception is if you're literally barefoot and pregnant, thus unable. The man in that case (and you better keep him around or you and your young children are dead of said starvation) in fact winds up doing your work in exchange for pussy. So much for your "feminism"; it only works out when there's a lot of economic surplus and hard manual labor is not required to eat, doesn't it?
Oh, but you say, I won't have kids and don't need a husband. Fair enough. In 20 or 30 years your body will be broken down from said hard work (as will the man's) -- now who's going to provide enough food for you to eat? You can't do it anymore yourself and you considered bearing children to be a "burden" unworthy of your "fine sensibilities"; well, unlike today that gets you dead as you get a bit older; nobody 20 years old and able-bodied with a working dick will choose you as the beneficiary of their extra work. You can't give them children anymore even if you managed to remain sexually attractive and you didn't create any children who, you hope, might have gratitude for the fact that you fed them off your tits for their first months of life! Oops.
Electricity? What's that? You banned "fossil fuels" which means no insulation, no fiberglass to make windmill blades and no solar panels. A crude metal windmill might produce a bit of power sometimes, and might be able to pump your well water. When the wind blows. But without insulation and the oil to go into a transformer you can't move said energy anywhere useful beyond your own small homestead, nor distribute it.
You get ill. You want to go to the doctor but he has no medicines; they're all made in some part with fossil fuels. Organic and inorganic molecular synthesis relies on it. Never mind IV tubing (vinyl and silicone), the bag to contain the IV (plastic), injection equipment (plastic), the mask you demand someone wear (blown plastic fiber) and more. Oh, and let's not forget anesthetics; you do know why the ORs were on the top floor of hospitals before they existed, yes? (Hint: It has to do with not being able to hear the screams from persons operated on without them!) Ban exploitation of fossil fuels and none of that exists and we're back in the dark ages medically. Congratulations, we'll send the Priest over to try to banish the evil spirits making you sick. It probably won't work.
Then it becomes cold. You know, winter? How did you say you were going to stay warm again? You didn't think about that, did you? You die -- you literally freeze to death.
Modern civilization exists because of the exploitation of carbon. I don't care if you like it or not; facts don't care about your feelings and banning exploitation of carbon will kill people in size along with collapsing the economy.
No person who argues for this has any business being anywhere near the levers of power, including RFK who has publicly declared he will do so. He has publicly declared himself a mass-murdering psychotic asshole who has no business in any policy role, period.
And so has every single one of the idiots who marched over the weekend.
You're entitled to be nuts and screw yourself as a consequence. Its a free country, and even taking personal actions that result in your own death is in fact a right you possess.
But you're not entitled to screw others, and if you credibly threaten to do so we all have a collective and individual right to stop you.