[Because in some men it is in them to give up everything personal at some time, before it ferments and poisons - throw it to some human being or some human idea. Thay have to. In some men it is in them - The text is 'All men seek for Thee.']
I think it means that we can't keep things bottled up inside for too long, we need to share certain thoughts or feelings with others before they start eating away at us. He uses the phrase "ferments and poisons" because he probably needs to get some stuff off his chest and he finds it possible by sharing it with the mute.
Just a guess....
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