Papa Bear, is not secure in his role. He feels you are too protective of your son, and are too involved- this "Threat" is that your boy won't be strong, but a "mama's boy". I went through the same thing a couple of years ago with my then 4 year old and my new husband. My husband was right. I did baby my son too much. I did a lot of no good work, and my 6 year old cries like a baby over too much stuff now. He backs talks me, but not my husband.
I would suggest, to your husband that he and your son get involved in a father son thing like "Young Marines, or Boy Scouts, or something of that nature. This way they have more of a one on one relationship, and so long as your husband is not physcially striking your son, or verbally abusive with name calling like "Stupid, or Loser" etc. Or teasing him in a mean way all the time-- Then your husband is probably more about being frustrated at your son's lack of playing alone- which can be a good exercise in character building self worth and self esteem in the right doses. He's your man, so you know better than I.
Your husband is not wrong in his desires. A lot of therapist often criminalize the man for being a male- and so long as your husband is not doing drugs, drinking, or other harmful behaviors, then there is no reason all this argument should be going on. He has a role to play in your boys life, and allowing him to do his job to raise that boy to be a man. Let him do it.
It is our duty as mom's to make sure we raise MEN, and that is why MEN were created to help us raise our sons to be men, and not over emotional wet blankets with no spine. It's a 70/30 split at this point, and your son looks to you for protection. Just as my son did. As moms we do our son's no favors. Life is tough and the sooner they learn to be tough, the better off they will be in the long run. That is your husbands job.
If I were you, I would sit down with my husband and lay out some ground rules. Like no hitting with a belt, and if your boy goes off the deep end in rebellion (as mine did) then find out your son's currency and use it. If it's privacy, take off his bedroom door, if it's his collection-- confiscate it.
Give your husband more power, and you hold the "Mother Bear Veto" where you can disagree with your husband, but you never discuss that infront of your son. Always a united front. We women do not do our son's any favors when we don't allow our men to teach our boys to be men. Even if it means a few spilled tears and a "That's not fair". he's 13.. it's time.