「Cock」with「mourning the dead」as FERMENTATION…understanding this meaning is simply a matter of visualizing a dead cock (i.e., a rooster, male chicken) in the summer sunshine after three days, noting that cock in China also was a euphemism for penis, and mourning one refers to the tertiary stage of syphilis with all its festering pustules full of corkscrew demons.
The reason yeast stops reproducing during FERMENTATION is that yeast waste product from digesting sugars builds up to toxic levels and kills them all (「family line dying out」), with YEAST committing mass suicide by literally drowning in their own shit: yeast excrement in grape juice is called「wine」when produced without the presence of oxygen, and「vinegar」when oxygen is present.
Right elements as「mourning the family line dying out, homosexual maggot」make sense, with the concept that all the yeast「maggots」will never survive, and instead will die out and kill the entire yeast colony due to being unable to reproduce and being smeared all over with their own toxic feces, and the feces of friends and neighbors (not unlike homosexual male humans, the sages are suggesting).
In Chinese an additional meaning of the right element is「mourning」the dead, as if to imply that the family line will die out under the circumstances of a homosexual male not reproducing while living at home with his parents. Right element is commonly thought to be「filial piety, honor your parents」and these elements as「child with old man」suggest a cycle of birth through death by old age and remaining with your parents one's entire life: during fermentation one generation of yeast lives with the next generation, all within the same container or 'household'…until all the yeast finally DIE DUE TO BEING COVERED WITH THEIR OWN EXCREMENT (that is, alcohol). Nonetheless, elements can also be interpreted as「cock with homosexual spermatozoa」descriptive of a YEAST INFECTION, in addition to a failure to reproduce an heir for the family line by commingling gametes of both sexes within a fertile environment.

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: yeast; leavening; fermentation
Japanese EDRDG: fermentation
Unihan extended: yeast, leaven