to leave DH after he encouraged our DC to kick me

Of course you should leave if you want to and think it’s for the best but I’d be so worried about what he’d be teaching my child when I wasn’t there to mitigate it. Would he hurt DC?

Personally I'm not keen on play fighting.
Neither was my ExH so not an issue we ran into.

But quite a few relatives would (for example) play Batman vs the robbers and as part of that game would say "let's kick the joker/your brother/mummy".

Not my thing and neither me nor ExH played those sort of games and if our kids did we shut it down pretty sharpish but I have seen it done and all adults and children seemed happy.

Very much dependent on the context and back story. It sounds like this was just play fighting if he and your husband were kicking each other. Fair enough if you don't agree with play fighting but if that's the case you shouldn't get in the middle treating your husband like he is a child and they are siblings. You should have waited to discuss it like a pair of adults when child wasn't in the room and come to some compromise.
However, if he is abusive and this is a way of using your child to abuse you it is a completely different story and there is no question about it, you absolutely do need to leave for the safety of you and your child.

It sounds like there are a lot of things which are making you wish to end your marriage, and this incident is the straw which has broken the camel's back.

Where you trying to stop dc from kicking dh? You said it had been happening all day

If there is violence of any type in the marriage you should absolutely leave him.

What did either of you do to stop your child kicking him all evening?

No parent should be encouraging their child to kick anyone. Not the other parent, not anyone else either. It is behaviour that should be nipped in the bud the minute it starts.

If my DH had ever encouraged the children to kick or hit me then I would have been furious, and yes, it could well have been a deal breaker because it is so utterly disrespectful.

You’ve focused on this particular kicking incident, which doesn’t sound terrible in isolation, so people are saying so.
But you also said There has been other occasions where he has encouraged our DC to hit me.
This makes it more serious because clearly this isn’t just a single incident of horseplay getting out of hand.

You think a grown man needs to be told not to kick people or even his own child?

Well based just on this one example of what you say was just playful horseplay, no I don't think you should end a marriage. Without the proper back story it's hard to comment any further than that unfortunately.

I wouldn’t leave my husband for this, but I would be very disappointed in him. The backstory matters – sounds as if it’s the straw that broke the camel’s back?

Sounds like your DH is mortally wounded by a small child overstepping and hurting him, and rather than dealing with it like a parent and adult human, he's decided to get some sort of petty revenge on him instead. He's then drawn you into it to make him feel better as he's not the only one being hurt by your child and he can say SEE! he does it to you too. Then the problem lies with your son not him.

Sounds like horseplay that got out of hand. Your DH needs to stop playing hitting and kicking games with your child.

I wouldn't leave for this.

I would be strongly encouraging both your DC and your DH not to kick people.

5yo is old enough to be firmly told off for doing this and to stop it. Your dh is encouraging him and no wonder he thinks it's a game. Yanbu.

Frankly I think it’s unacceptable to be playing kicking games with a small child who is unlikely to be able to distinguish between play and not play, and will end up getting into trouble for it at school/nursery. And abhorrent to then encourage the child to kick their other parent.

If it was playing and it was in jest, it’s not worth leaving him but just asking him privately not to encourage your son to kick you because it hurts/teaches him that’s ok etc (not in front of your son).

If there’s a back story whereby your partner uses your son to abuse you because he can get away with it if your son has instigated it then absolutely get out of there because not only will he continue to do this but he will teach your son to do this!

Yes you should leave if you wish however be aware he will get one on one time with the child as he won't be seen to be unfit for pulling shit like this my ex told the children they didn't need to listen to me or do as I said led to a very adversarial relationship with my son until he matured enough to work out his dad didn't WANT him he just wanted him to hurt me

Be prepared for therapy

I do think the back story will play a large part in a decision here. But if your gut reaction was this is wrong and to post on here then get out. Don't let things cool down/make excuses/sweep it under the carpet, etc, because the longer you wait the harder it will be to show your son the right way to treat those we love.