While the impression may be that Ian Stewart resigned to the decision of Andrew Loog Oldham to take him 'out of the picture' of The Rolling Stones for rational reasons, there were -of course- emotional aspects too. Here's what Stu's wife, Cynthia Stewart (born Dillane), with whom he married in 1967 and who was, spicy enough, a personal assistant to Andrew Oldham for five years, has to say about the topic:
Whatever Stu or anybody else said, he did care about being relegated. He had enough to worry about because he was so painfully shy. But the bottom line for Andrew was that Stu's face didn't fit; Andrew loved the pretty, thin, long-haired boys. Stu felt bitter, not because he was not up there on stage, but about the savage way he was kicked to one side.
Stu was contemptuous of Andrew - understandably as he kicked him out of the band. Stu just thought it was Andrew who was responsible for the decision. Stu was deeply hurt because he wasn't good looking in the genre of the day. I don't think he felt anything except hurt. Stu was very honest, he was painfully shy, but he always said what he thought.
Adapted from the following sources:
Bill Wyman, Stone Alone, Penguine Books, 1990.
Andrew Loog Oldham, Stoned, Vintage, 2001.