[Gurthang]

I agree, the rings were made by elves, which only one ever was able to overcome a balrog. They would not have affected him enough to do much good.

And another thing, the rings were made to aid in the creation of beautiful things, not for attacks and war. They may have been able to defend(Lorien and Rivendell) but could not have repelled any creatures. The fear was probably caused by the heavy resistence that the elves caused when anything evil tried to enter the woods. They loved them dearly, thought them sacred, and would not suffer any but their kindred to enter.

Thranduil's people did not necessarily love Mirkwood, and they only kept a portion of it clean.(Beside the fact that it was enormous.) They would not have cared who entered, as long as they did not bother the elves.

But Galandriel's people cared for the woods as a living thing. This was why everyone feared to enter the forest of Laurelindorinan.