You are also correct in it was disrespectful and wouldn't happen if they were face to face.
BUT I do think an apology is enough, regardless of being called out on the internet. An asshole behind a keyboard doesn't use the same keyboard to say how they were wrong.
People make mistakes and when you do it on the internet it quickly amplifies.
You may say I am a little bias because I have met Corey in person. He was boarding a plane and I ran up and introduced myself after having heard one of his talks. He took his time while others boarded and was very courteous and friendly. So I trust in his apology and that he isn't an asshole in person or behind a keyboard.