Interesting musings but I think the point here is that there are certain parts of the aircraft directly facing into the air flow. Whilst you are quite correctl that rubber is a good insulator and being black would also absorb any radiant heat these are of insignificant consequence compared with an airstream passing over the surface at 80+ knots at less than freezing. Any residual heat will be lost very very quickly and of course in cloud there is not likely to be much radiant heat around.
Boots as you will know are rubber and in the "right" conditions accumulate ice and a significant rate.