Mr. Steak posted:

誰だ　このイカついおばさん

He *is* calling her rude, but on top of that, the word he used for woman (obasan) implies that she's [literally: old. figuratively: ugly], so it's also directly challenging her vanity. That's a word that can only be polite if you use it to address a clearly elderly woman whose name you don't know. Any other woman would be highly offended to be called this.

And then Coby ups the anti by calling her a ばばあ which is another level higher in the old/ugly hierarchy, lol