That's not a bug but a feature request.
And one that asks to fix the wrong thing - nothing is wrong with autoswapping. You should not be allowed to swap with the NPC only if it would place him outside his preferred position - i.e. shopkeeper away from the door or smith outside his smithy.

What should be changed is the "getting angry and attacking" part - while nobody asked you to walk around bullying poor demented ratlings and other random dwellers, them getting angry enough to publicly attack a much stronger PC right there in the village is too stupid from them: the probability of getting angry should decrease to 0 if your character is much much stronger than the displaced one (or has a high Appearance score).

I would classify this as "unintended oversight of recent new feature", and fixing a problem with a feature is a bug. The goal of the feature is convenience, which it's great at, but this one particular case forces Dwarftown traversal to become a big hassle if you always have to watch out to make sure the ratling isn't in the way. As a bonus, it seems like the logic already exists for certain NPCs in Terinyo.

As the ratling is demented and likely significantly tainted by chaos, I see no reason why character's strength would deter him from doing something crazy.

(on a related note, I used white necromancy for the first time and my homunculus almost bled him to death, but he's peaceful again. hopefully quest still works!)

I kinda agree that occasionally he becomes hostile due to swapping too early. Keeping a counter allowing to swap with no or with minimal risk several few times would probably make sense.

Agreed.