He bristled when he was teased, and got angry and embarrassed. He sometimes stumbled over his words, and tried to give half-hearted comebacks but was nowhere near as pithy and witty as he was as Spider-Man. He was frustrated by it, and dwelled on it frequently because he wanted to be accepted and to have friends. If that's not how real bullied geeks often behave, then I don't know what is. He had the means to stand up for himself of course, but couldn't act out using his real strength because of his responsibilities as Spider-Man. I don't know what Ultimates Parker did, but if he punched the bullies out or whatever, then that's not a realistic portrayal of a bullied kid. That's wish-fulfillment.