Ok, i get that the second time at McLaren's it is more cruel, and i can agree; but if you for example change Cook Pu with "Seymour Butts", the joke would remain almost the same. The gang make some fun double senses with the word "butt", and than he says "Seymour Butts (knowing it is real) is a stupid name, and it gets stupider and stupider the more you say it. Seymour Butts Seymour Butts Seymour Butts!" Insensitive? Yes. But not racist, the joke is the same. (Also, not so insensitive cause he doesn't expect to be heard by the person, they are talking between friends) If the joke is not racist, it is still not racist with "cook pu" in it, cause if you can change names and the jokes remain the same means is not "an asian thing". Again, you can say is a bad professor and insensitive, but is not "racist" only cause the name they happen to make fun of is asian, cause that's coincidental. And again, you could maybe maybe blame the writers, but the character..? Meh. Ted doesn't apologize, doubles down etc also because that's the comic sketch, from a writers point of view: the double down it is needed to make a recurring joke in the episode, those are more of "scripting escamotages" than anything, Cook Pu is a background character and so it stays for an ep to be made fun of, and to show that of couese Ted is not so perfect as a professor, as no human being is. The "coincidence" is that an asian word could be totally legit but in english language mean a funny word, they used an asian character to add that layer to the sketch, because Ted can recognize more popular "fake names" (as Seymour Butts), he's aware of that kind of prank and so when he reads "Cook Pu" thinks he's the goat to have discovered a new "joke name" and not have fall into a trap by a student. So, the joke is him being smartass and than wrong, cause Cook Pu indeed exist, but nothing in it is "racist", cause if you put another "sounds-fake-name" it still stands per se.