If you are using words that are neuters specifically, then you have to use neuter suffixes. In this case, rádo.
Of course, you can say má rád/ráda if it is a boy/a girl and you use masculine/feminine words. But you can't say To dítě nemá rád sýr.
"And when it comes to neuters, don't they default to the male (rad) gender if the gender is not known?"
I think that you might be confusing grammatical genders and 'real-world' genders.