They have no idea. Just something they heard. What would 'bad' even look like? I try not to mix natural and synthetic, but Hetman (synthetic) says it's ok <shrug>. These days I rock Lamp Oil. Gallon bottle: $25.00, been using it for almost two years. About 1/4 way through the bottle and I am not stingy with the stuff at all. If you go that route you can find it in your local supermarket, just don't get the stuff with scent, mosquito repellent, or day-glo colors!
I can’t find the lamps other than on eBay (about 300-400 per if working, but apparently you can still get the mineral oil for it on amazon.
Rain Lamp Oil - 32 Ounce - Unscented https://www.amazon.com/dp/B00QXI7ZH4/ref=cm_sw_r_cp_api_i_nthWDb2E5MHWD
For the fuel for torches I guess I'd start by looking at using fuel for tiki torches. Not sure how it would work in a bowl but whoever you're getting for your pyro work should know.
I do not envy your situation. Get a few tiki torches and use an oil like this. This is the kind of thing my family used to do and it should help at least ward them off. Other than that, go full scorched earth tactics (BURN EVERYTHING) or wear a bee suit.
That's shitty man. Try the torch and let me know how it works for you.