Caroline, I agree with you that iodide is an essential nutrient and it could be that its RDI has been set too low.

However, I am a bit puzzled by what is in your link (quotes taken from it, my emphases):

"These halides cause health problems, including cancer, and include fluoride, bromide and chloride"

Chloride is an essential nutrient. It is needed for (among other things) maintaining acid/base balance, transmitting nerve impulses and regulating fluid transport into and out of cells. I know of no evidence that it is a carcinogen.

"Even worse, your body becomes starved for iodine when you have these metals in your body."

Halides are not metals - this is elementary chemistry.

For me, these errors are not a source of confidence about the content of that site.