It is the age.
Kids this age do not necessarily 'know' how to play interactively... and are still into "parallel play."
Developmentally, you need to consider 'how' kids play at this age.
And they are NOT 'rocket scientists' socially, at this age.
Yes, they hit at this age. Too.
Some kids being more physical than others... and have more or less, communication ability or talking ability... AND kids this age do not even have fully developed "emotions" NOR do they even know how they feel, much less have the ability to succinctly say it, nor with the proper wording/sentences.
AND... kids this age, do.not.have.... fully developed "deductive reasoning" either.
Now if the play-dates are not enjoyable, then stop.
Getting together once or twice a week, with the same Mom/child, to me, is a lot. I would get burnt out myself. Ick.
And well lots of parents have 'excuses' for their kid. Or it may just be because they DO NOT know, how else to 'explain' their child's behavior.... either. So they come up with a generic 'reason.' Hence, it may seem like 'excuses.' Or do you want a whole litany of reasons? Which may or may not be valid?
Behavior... is often because of MANY factors all at one time. Never an isolated thing.
And it also has to do with... the 'dynamics' of the kids themselves and their personalities.
NOT all kids, get along.
It is normal.
Nothing wrong with that.
And not all kids like each other.
Normal.
No one has to like, everyone and every single person. Adult or child.
It seems, you need to just stop, getting together.
Not all play-date associations, are productive or enjoyable by the child or parent.
Fine.
Find other parents/children that are more, in line with your own, approaches to things.
Drama and negative interactions, can be avoided. or stopped.
See what is best for you and your child.
I personally would NOT have a kid that beats up mine, in my house. Or a parent that is at polar opposites, of what I feel is appropriate or not. Even if it is an age related phase.