"Is it right using people only for your own pleasure?"

I take it to be an Andersson cipher about human society and existence. Anyone who purchases and sells is using another for their pleasure, although mostly that pleasure is undercut by misery.

In the midst of winter, I found there was, within me, an invincible summer

But you realize he was talking about the instrument that made music by burning people, don't you? Cause that was pretty obvious, but maybe the subtitles were bad in the version you watched.