'Dog Whisperer' Cesar Millan -- Simon Cowell Needs to Teach His Bitch Some Respect

"Dog Whisperer" Cesar Millan says Simon Cowell's dog got WAY too close to his baby on the beach this week -- and he better get his bitch in line ... or the baby could be in danger.

We posted the pics Monday of Simon on the beach in Miami with his newborn son and two Yorkies -- and one photo shows a dog sniffing the baby's face.

Cesar called in to "TMZ Live" today to explain why it's a TERRIBLE idea to let your dog get so close to a baby ... and it's pretty shocking. Take a listen.