His clear disdain for a fairy was the first time Grimshaw actually displayed any kind of negative emotion at all. Even then, he was not entirely dismissive of it, nor did he excessively degrade fairies. Instead, he, in his own way, asked Bob if a fairy could tolerate the influence of his presence.
Besides Bob, Grimshaw did not seem to treat the others in the crew as being anywhere near his equal. That was likely why he did not even react negatively to how Bob repeatedly insulted him. The effect he had on others was not lost on him, which is why he found the notion of a fairy being Bob's captain so interesting.
"The question is, will you be able to tolerate the consequences of crossing the captain?" Bob asked dismissively. Since Bob had decided to follow the captain, how could he be ordinary? How many fairies did one see sailing across the universe in a wooden ship? One. Just one - the captain!
