I think some young adults have absolutely lost the run of themselves and how they imagine they can behave and what will be tolerated by those who care for them.
A couple of years ago my friend had a run in with her son who thought he could move his girlfriend in because she had fallen out with her flatmates because they were jealous of her??.
My friend told him absolutely not. Both sets of grandparents visited regularly and her daughter didn't particularly get on with her as she was a bit of a smart mouth, and this was her daughters home, so it would not be happening.
Anyway he was incensed at being told No, was very rude to his mother and she told him how he spoke to her was completely unacceptable.
He told her he didn't care and was moving out.
She told him at 25 he must do what he had to do.
He moved out and she wished him well but didn't chase him.
Her husband absolutely supported her and told him he was completely out of order.
He doubled down.
She was very hurt and upset but she said that if the cost of a relationship with him was verbal abuse, then the price was too high for her.
It caused a lot of chat among her circle of friends because as mothers is it a relationship at any price with our children?
Are we to be held to ransom by them if we don't behave or agree to everything they want?
Girlfriends/boyfriends moving in?
Made to feel uncomfortable in our homes by them constantly wanting to stay over?
Deposits for houses?
Free childcare?
Constantly being expected to have grandchildren for weekend after weekend?
Held hostage by them as we age?
These are constant threads on MN.
Anyway, he was in a full strop for months and didn't call.
Despite my friends huge upset she didn't bend.
He turned up one night out of the blue and apologised.
The girlfriend was gone and a nightmare to live with.
He had moved on to house share with a few friends and was getting on well.
My friend happily accepted his apology and no more was said. He comes home regularly and 3 years later they have a great relationship.
He respects his mother and realised she is not someone that will accept being treated poorly by him.
I have 2 sons in their 20's and I certainly wouldn't ever want them to think speaking to me like something on their shoe would be tolerated.
I have far too much respect for myself and they know it.
I think the OP's son has crossed a shocking line verbally abusing his grandparent like that, and I actually do not know how it can be recovered from, without an abject apology in person.
That his grandmother has been so ill, further exacerbates the sheer awfulness of this.
The girlfriend is obviously the utter dregs, but her son's behaviour towards his grandparent really is quite shocking.
Some seem to expect the independence and freedoms of adulthood without the dirty business of paying bills, and sharing the responsibilities that are attached.
As adult children they are not entitled to think their family home is theirs to use as they please, particularly while working.
Rent is expensive and affords great freedoms.
Paying pocket rent at home does not mean you have the same advantages, like endlessly entertaining boyfriends and girlfriends.
Some struggle with this since Covid.