He want to get things off his chest and it's the only way he can get himself heard.
5 seconds sound clip from the Meet John Doe (1941) movie soundboard.
You can hear this line at 00:11:12 in the DVD version of the movie.
Quote context
[...]
- Now, then comes the drama. He meets discouragement.
- He finds the world has feet of clay, his ideals crumble.
- What does he do? He decides to commit suicide in protest against the state of civilization.
- He thinks of the river, but no. He has a better idea: The City Hall.
- Why? Because he wants to attract attention.
- He want to get things off his chest and it's the only way he can get himself heard.
- So?
- So?
- So he writes me a letter and I dig him up.
- He pours out his soul to me.
- From now on we quote: I Protest, by John Doe.
[...]