Resistor spark plugs reduce electromagnetic interference with on-board electronics. The only electronics in a carbed Bonnie is the CDI unit. Older CDI units on other bikes are pretty robust devices containing just thyristors and other electrically robust components, but your CDI is described as "digital", meaning it contains some more delicate electronics like memory chips, etc.
I've been running non-resistor plugs on my XV1100 for years, even though that has a similar digital ignition system as well and resistor plugs were standard on it, with no ill effect so far.
I wouldn't do it on the EFI models though, just in case.
This is what NGK have to say about it: