People say this with such confidence in how they'd actually feel (and probably such confidence that they'll never be in that situation).
In reality, it's ok to still very much love your child. Very few people commit 'abhorrent' crimes without something having gone horribly wrong in their own lives along the way - their own trauma or abuse, an addiction, mental illness, often all three and more. As a mother it's ok to see the hurt to them as well as the hurt they've caused. You might be the only one, and that must hurt too.
What's not ok, especially if it's abuse of children or vulnerable people, is letting him back into family events, or giving him any information at all on family members who've chosen to cut ties, or anyone who would potentially fit a victim profile.
Judging is easy from the outside, but it's ok to be mourning the hopes you've had for the child you love, and wanting to hug them on the worst day of their life even while the thought of what they've done makes you ill.
I hope you are able to speak in person with others who've been through this before, and get some support. Don't do anything in a rush, and think very carefully about which friends and family you talk to, it's so private and ripe for misunderstanding, arguments and really poisonous gossip.