You don't get it. It isn't us that believe that God predestines babies to go to Hell, it's Calvinists! It is your own doctrine that you're arguing against, not ours!
Calvinism DOES NOT teach that babies are innocent! It teaches that they are all born in sin and totally depraved! Calvinism likewise teaches that the elect are not saved because they are innocent nor because they believe nor for any other reason. Calvinism teaches the opposite! It teaches that people believe because they are elect, not the other way around! And, in a manner consistent with that teaching they also teach that if a baby dies then whether it will end up in Heaven or Hell depends on whether or not the baby happened to have been one of the elect and upon NOTHING ELSE!!!!
“God is moved to mercy for no other reason but that he wills to be merciful.” (John Calvin, Institutes of Christian Religion, Book 3, Chapter 22, Paragraph 8)
“… predestination to glory is the cause of predestination to grace, rather than the converse.” (John Calvin, Institutes of Christian Religion, Book 3, Chapter 22, Paragraph 9)
“Therefore, those whom God passes over, he condemns; and this he does for no other reason than that he wills to exclude them from the inheritance which he predestines for his own children.” (John Calvin, Institutes of Christian Religion, Book 3, Chapter 23, Paragraph 1)
“We cannot assign any reason for his bestowing mercy on his people, but just as it so pleases him, neither can we have any reason for his reprobating others but his will.” (John Calvin, Institutes of Christian Religion, Book 3, Chapter 22, Paragraph 11)
"All are not created on equal terms, but some are preordained to eternal life, others to eternal damnation; and, accordingly, as each has been created for one or other of these ends, we say that he has been predestinated to life or to death. (John Calvin, Institutes of Christian Religion Book 5, Chapter 21, paragraph 5)