As a family we are very into rough and tumble playing, although DH and I have had to stop practicing our martial arts together (both black belts) because the little one cries even though we're smiling and laughing.
In fact, it tends to be DH, DS1 (4 years) and DS2 (18 months) wrestling together. I sometimes join in but DS2 really takes against anyone wrestling with me (it's a phase, DS1 went through it too), so I usually just watch and referee.
We've had occasional bumps and tears but certainly not every time. Once in a while DH will accidentally hurt DS1 but he is mortified and apologises and they make up. I actually think it's a good example to set to DS1 about how to act when you've accidentally hurt someone.
When they start to get overexcited we stop and tell them to calm down. Every so often (usually when teething), DS2 starts biting and he is taken away for a time out - we are very strict with that.
It is almost always the boys that initiate the wrestling. They love it.
I can't tell if OP or her DH is being U though. If OP is micro managing how her DH interacts with his son then I can see her DH being pissed off. But if her DH really is being too rough and not controlling it and really hurting her DS then he is being U.
On the other hand, I really wish that I'd been told as a child that small bumps and scrapes (the kind that hurt for 30 seconds) really aren't the end of the world. I was far too anxious and accident-averse as a child, and it's only when I started karate when I was 23 that I realised that being hurt isn't the end of the world. Yes it hurts a bit to get a bruise, but it doesn't last. Both my DSes are much more of the "fall over, rub your knee/arm/etc. better and carry on" than I was and I like that.