Its the dose that counts
I do not wish to turn this into a political discussion, but treating your clothing and hammock with permethrin is not going to poison nature. It will repell, and possibly kill, ticks, skeeters, biting flies, ants etc but there is a world of difference between the limited application of an insecticide to fabric and the tonnage applied to crops each year.
A possible carcinogen? Maybe so. But we do know that West Nile virus is a serious disease. Likewise Lyme disease and RMSF.
If one believes strongly in not using insecticides and pesticides (including repellants) then you are free to not use them. You are also free to lobby against their application wholesale to crops.
There are others (including me) that are willing to balance the potential risk against the real benefits. My application of permethrin to clothing and hammock will in no way aggravate or harm you. Go in peace.