Do some people know someone else's preferences better than they do?

I’m sure you and this guy get along swimmingly.

How is someone who puts a lot of stock in traditional dictionaries similar to a nihilist?

I am merely saying that the “commonly understood” definitions of commoners are meaningless to me. Unless they are objectively written out, in which case I shall consider them. (Hence my willingness to entertain your definition, which is not written in the OED, but various modern dictionaries).