Doesn't really make sense since if it can talk to it, it will mine on it.
If it can't mine on it, then that would be coz it can't talk to it thus it can't tell it to turn the led off.
It is possible to enable/disable a device using the USB menu. I have sometimes slow nanofurys because of several reasons. To find them I disable and wait. Then I try to find the cold one. If the LED would be switched off, it would be much easier.