I am one in favor of letting a lesson be learned as needed. We have cats ( we lost one last week *sniff* so now it is only 2) who have varying degrees of tolerance to the baby. But they all seem to understand that he is a baby,,and he gets away with way more than the older kids.
If he does cross the line, they let him know by either growling/hissing/yowling or taking a swipe at him with their paws. They learned pretty quick that the vocalizatins were what worked,,he would burst into tears. If they swat at him, he thinks it is wonderful game! ( I wanted to add that Josh has only had a handful of scratches on him,, and they were from playing with the kitten)
But we do spend a lot of time talking about soft touches, and I think Josh has caught on partly because the cats stick around when he is being soft, but they take off if he isn't so soft. I count on the cats to set their own limits,,and head for high ground if he crosses the line.
Interestingly, one of our cats is not quite a year old. He was a tiny nubbin when we brought him home,,and right away he thought that Josh was the other kitten in the house. They play forever, sleep snuggled up together,,it is so cute. The only problem is when kitten wants to groom the "baby kitten" and wakes him up with that rough tongue in the middle of the night..we will usually end up locking the kitten out of our room if he is too affectionate and wakes his baby!