In the novel "Stranger in a strange land" by Robert Heinlein there is this passage:

’Gratitude’ is a euphemism for resentment…The Japanese have five different ways to say ‘thank you’—and every one of them translates literally as resentment, in various degrees…English is capable of defining sentiments that the human nervous system is quite incapable of experiencing.

You can find quotes similar to this one in some of his other books too.

I really do not understand the first part of this quote:

’Gratitude’ is a euphemism for resentment

Also, the part about Japanese language is definitely not correct.