And being short is a symptom of achondroplasia, along with many other painful issues. It's a joke about how he is unable to do something to any kind of reasonable standard, because he has a disability.
I bet dinklage would find it funny
Maybe he would. Maybe he's heard so many shit short jokes in his lifetime that it would be just another asshole who thinks they're hilarious and original. And maybe his snow white dwarf comment was less about the mythical creatures as much as it was abour society's portrayal and exclusion of people with bodily differences. You, much like the person who posed as him on Twitter, do not get to make that decision for him.