Husband and Son Fighting

I cant seem to get clear on what to do about a situation in our home. My son and husband get into some really instense arguments with each other. My husband has made it very clear to me that he wants me to support him no matter what and not to undermine him in front of the kids. There has been a couple of situations lately where I will jump in and start taking my sons side because my husband will be very demeaning and throwing out all sorts of insults trying to motivate him and instead hes just making him feel bad about himself. I can see it happening and I know its obviously not working and we need to try another approach and just talk to our son later when emotions arent so high. How do I stop a fight from escalating and how do i honor my husbands wishes when I clearly dont agree with what he is doing in the moment. Thanks