So? Would we make any noise if it was the man who was 42 and the woman was 23?
I dont't think so. Us Asians have long held prejudice against an older woman going out with a younger man but praise old men for going out with younger women.
Look at it this way - the man is 23 years old. He is not some underage kid who doesn't know anything. Legally, he CAN take his parents to court - he no longer needs his parent's permission for anything and is a grown man. Similarly with the woman.
IMHO, I feel that his parents need to learn to let go and let their son make mistakes on his own OR live his own life for himself. If they are in love, who cares about age?