One reason would be God's revelation of Himself, through Jesus Christ, as "Father." Clearly the distinction was important enough to Jesus that he used a word with gender (in the grammatical sense) rather than "parent," "ancestor," "progenitor," or another word of neuter gender.
A non-Christian believer in God, of course, would probably not find this point very relevant!
Agreed.
It seems that it should be a fairly short debate:
Q: How did Jesus describe God?
A: As his father