Honestly I can't see a direct connection between judging Taichi and Sumire. I mean, I think Sumire has been bitchy, it is a matter of fact to me. And I think that was the purpose. No hate here.
Surely the indirect implication of her behavior has been as often happens, first, to flash out Kanade's resolve and backbone handling her, and last to point out another Taichi's inner little step.
In response to a question about his high-popularity among the girls he stated that he prefers to chose instead of being chosen. In context, he implicitly admitted of being aware of his popularity, but that wasn't the point there. And in any case, he is popular and it's not something he should feel guilty for.
The main point, to me, was that he had a girlfriend once whose he didn't care and at that time apparently he even didn't care not caring for her. In this episode he made clear that he won't make the same error twice. And, I admit, I couldn't avoid to be pleased by that.
