I don't know why creationists never get around this argument but...
1. Sure, one step in our ancestry might have been a monkey. But menkeys do not have to be extinct just because we evolved from some ancient primates. I mean, just look at your parents. After you are born, should they cease to exist? No, and in fact they might still produce more children.
2. Half-man/half-monkey: If I should take your words at face falue then... gibbons, orangutans, chimpanzees, gorillas, bonobos are the half-man/half-monkeys still living now. They (might or might not) represent stages in human evolution.
Anyway, just a question, do you know the difference between
monkeys and
apes? Creationists seem to be deliberately mixing the two.