Why would you make fun of them if you don't think these traits are bad?

As another autistic person, I didn’t understand this instinctively so I can actually articulate an answer for you.

The reason you make fun of your friends is to reinforce the shared understanding that you are friends.

I’ll try and come up with an analogy.

There is a king who keeps very tight security around him at all times. Everyone must be disarmed before they enter his chamber, because he doesn’t trust anyone. Except for one man. There is a knight in this king’s court who is allowed to wear his sword into the king’s audience chamber.

Why? Well, because it is an honor to be trusted to this degree. And why does the knight bring the sword in? Because every time the king chooses to allow the knight’s sword into his presence he reinforces his own trust in the knight. He reinforces the pathways in his brain that consist of this trust.

That’s the knight’s reason.

Why does the king allow the knight to bring the sword in? Because every time the knight chooses not to draw that sword and kill the king, he reinforces the part of his brain that is loyal to the king. That is the king’s reason.

The king and the knight both benefit from their relationship; they both want it to be strengthened.

So they allow the creation of a situation that only works if they’re friends, because this disambiguates the relationship in their mind.

I know it’s not the best analogy. But it’s about competing narratives in the brain, and how presenting a scenario whose resolution into one decision or the other reinforces the narrative that matches the decision.

If we are friends, and we’re hanging out, and I say something insulting to you, I’m doing that because the insult gives you an opportunity to reaffirm our friendship by choosing to take it lightly and laugh at it. The word “reaffirm” here encapsulates the logic in the last three paragraphs preceding this one.

The insults are the sword in the audience chamber. They are a threat. By dismissing the threat, one reaffirms the relationship.

It makes more sense in the context of demonstrating to a third party that two people are friends — say if that third party was thinking of playing them against one another — and to apply it to two friends alone you just need to remember a human brain runs thousands of little minds in parallel.