AIBU to think my 3-year-old isn’t being “mean” and that family should stop taking it personally?

Unless you are in a large house he's probably overwhelmed and ratty. He has to learn he can't be rude to her though.
Is she a bit full on and have you spent lots of days together? He's not been taken out of nursery to spend time with her or anything?

Why are people talking to 3 year olds in long complicated sentences about feelings??
He has no idea why he feels cross but it's unlikely to have anything to do with your MIL.
"We don't do that/say that" and ignore any further rudeness.

He’s being rude and unkind and you need to tell him that’s not nice behaviour

Exactly. I think the adults need to grow up a bit!

Small children are famously fickle. I'd say "oh that's not kind, that might make Granny very sad" but I wouldn't make a big deal of it.

Yeah. People wonder why the behaviour in schools is out of control. This rubbish is why.

I'd say he's picked up on the fact that the adults think MIL has outstayed her welcome.

Really? You'd end a planned family visit early on the back of a 3 year old? Stuff what the adults want if they do want the visit to continue

I wouldn't. I would acknowledge potential feelings of overwhelm but explain that grandma is here for her visit and staying as planned.

That’ll be why your husband is defensive. My parents live far away. My husbands are round the corner. When my kids were tiny, I hated that the relationship they had with my parents wasn’t as close/involved and in the past I know I’ve been defensive about that. But now they are older they are super close. It’s just different but it’s not worse

I imagine he’s probably getting some positive reaction from OP too even if she’s unwilling to admit it. A child who knows that behaviour is wrong and receives a single message from both parents doesn’t keep doing it.

There’s two stages to these events.

The first is to tell ds that what he’s saying is rude and upsetting for nana.
The second is for the adults to then not to take this toddlers behaviour personally and to give ds space.

Your H needs to grow up!

Our granddaughter, when she’s tired always wants me (we look after her one day a week). She will say to DH “No, I want granny” and push him away. Dh doesn’t get upset by this, he just brings Grandaughter to me!

No. I’d acknowledge them and talk to him about it. But I wouldn’t pander to them and give in to them.

He's old enough to understand that what he's saying isn't kind and it isn't something I'd allow.

I wouldn’t expect a 3 yo to be lying and telling his grandmother not to sit somewhere. It’s bad behaviour and you do need to nip it in the bud before he begins to treat other children that way too.

So you’d just ignore his feelings?

I remember my son at 3, fetching visitors’ coats when he’d had enough - he’s a lovely adult now.

MIL & DH are taking it too personally, I’d not end the visit if I didn’t want to but would make more time for me and DS, encourage MIL and DH to grow up and manage their expectations, and not worry, it’s all normal.

You can’t have a three year old ruling the roost. I sympathise with his views on having a guest for too long but no, I wouldn’t allow or pander to that behaviour. It’s not up to him to start policing who you have in the house and when.

It sounds like he's getting a lot of attention when he is unkind so obviously he's going to continue to tell lies and say unkind things because he gets your attention and 1-1 time. Maybe it's time for some consequences?

Exactly. 3 is plenty old enough to understand. You need to tell him that while you appreciate the house feels crowded, it's very unkind to say things like that to people and out of order to lie.
I have a 3 year old and would never tolerate that behaviour without challenging it.

You are doing a lot of good things.

Time for consequences.
Remove him from the room and tell him he needs to have time away from everyone because he is being rude.

I agree. I have a 3 yr old and she doesn’t get to say “you can’t come in” or “you can’t sit down” to people and have me brush it off as “well that’s just how she feels”. It might well be how she feels, and I wouldn’t dismiss that, but she doesn’t get to order people around and be mean. P

He is behaving badly though, even if he is overwhelmed. He is not too young to be taught that saying some things is rude, mean, and will not be tolerated. You need to be on top of it.

Children's don't have a filter or know what way to process emotions.
He wants her to go home, he wants peace without DGM.
I'd tell him not to be mean, I'd take his toy for his behaviour, I'd also tell DGM to go home, DH needs to grow up.

You can absolutely talk to him about "only kind words" and "words can hurt someone's feelings" etc.

But he does sound overwhelmed a bit.
Your husband sounds like toddler himself 🙄.

Remove him from the room every time he is rude and have the conversation.

Also ask him how he is feeling.
Ask him is he feeling the visiting is going on too long.

Help him understand his feelings and help him find the words.

Could you take him out for a walk.