Ditto what Audrey said word for word.
Its natural for children to cry. It's how they work their emotions out. Your husband needs to keep in mind that your son has not developed the emotional tools yet that we as adults use to control our emotions and the ways we react to situations.
And I'm sorry, I don't mean to sound rude here. But it always makes me laugh when someone says to their crying child "stop crying or you'll get a spanking." Or, "Stop crying or I will give you something to cry about". Um, hello, that is only going to make your child cry more and eventually that child will start to resent you. Like spanking him is going to stop him from crying anyway. (and yes, my own father used those lines on me and guess what happened? I cried more)
I really hope you are able to talk to your husband again and get it through his head that his reactions to the situations do not help your son. It is his role as the "father" to be a role model to your son. Threatening and scolding is not the approriate response here. (Unless he wants his son to harbor resentment towards him later in life)
Good Luck!